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Radio on Board

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Frequency vs. Wavelength

There are different ways to indicate where to find a certain station on a radio dial. For example, we could say that a station is operating on 9680 kiloHertz (kHz), 9.68 megahertz (MHz), or on 31 meters. And all three ways would be correct!

Radio waves are transmitted as a series of cycles, one after the other. The hertz (abbreviated Hz) is equal to one cycle per second. Hertz was named after Heinrich Hertz, a German physicist [1857-1894] who experimentally proved the existence of electromagnetic waves. You may have noticed that the electric power supplied to your home is rated at 60 Hz. Electric power is distributed as alternating current (AC), meaning it goes through a cycle of changing directions of flow. When we say that electric power is "60 Hz," we mean 60 cycles per second (in which time the direction of flow changes 120 times).

Radio waves go through far more cycles in a second than electric current, and we need to use bigger units to measure them. One is thekilohertz (kHz), which is equal to 1000 cycles per second. Another common one is the megahertz (MHz), which is equal to 1,000,000 cycles per second----or 1000 kHz. The relationship between these units is like this:

1,000,000 Hertz = 1000 kilohertz = 1 megahertz

Radio is usually thought of "beginning" at frequencies of approximately 5 kHz, although most available receivers can only tune down to about 150 kHz.

The term "wavelength" is left over from the early days of radio. Back then, frequencies were measured in terms of the distance between the peaks of two consecutive cycles of a radio wave instead of the number of cycles per second. Even though radio waves are invisible, there is a measurable distance between the cycles of electromagnetic fields making up a radio wave. The distance between the peaks of two consecutive cycles is measured in meters. The relationship between a radio signal's frequency and its wavelength can be found by the following formula:

wavelength = 300 / frequency in MHz

According to this formula, a frequency of 9680 kHz would be equivalent to a wavelength of 30.99 meters, which we would round to 31 meters. Thus, 9680 kHz, 9.68 MHz, and 31 meters all refer to the same operating frequency!

As the formula indicates, the wavelength of a radio signal decreases as its frequency increases. This is important because the length or height of various types of antennas must often be a fraction (usually one-quarter or one-half) of the wavelength of the signal to be transmitted or received. This means that most antennas designed for frequencies near 4000 kHz will be physically much larger than antennas designed for frequencies near 30 MHz.

Frequencies are seldom given in terms of wavelength anymore. However, certain segments of the shortwave bands are referred to in terms of "meter bands" as a convenient form of shorthand. For example, the term "10-meter band" is used to refer to the ham radio band that extends from 28000 to 29700 kHz. The following is a table of the most common ham radio and shortwave broadcasting "meter bands" found on frequencies below 30 MHz:

Meter Band Frequency Range and Use
160 meters 1800-2000 kHz ham radio
120 meters 2300-2498 kHz broadcasting
90 meters 3200 to 3400 kHz broadcasting
80 meters 3500 to 4000 kHz ham radio
60 meters 4750 to 4995 kHz broadcasting
49 meters 5950 to 6250 kHz broadcasting
41 meters 7100 to 7300 kHz broadcasting
40 meters 7000 to 7300 kHz ham radio
31 meters 9500 to 9900 kHz broadcasting
30 meters 10100 to 10150 kHz ham radio
25 meters 11650 to 11975 kHz broadcasting
22 meters 13600 to 13800 kHz broadcasting
20 meters 14000 to 14350 kHz ham radio
19 meters 15100 to 15600 kHz broadcasting
17 meters 18068 to 18168 kHz ham radio
16 meters 17550 to 17900 kHz broadcasting
15 meters 21000 to 21450 kHz ham radio
13 meters 21450 to 21850 kHz broadcasting
12 meters 24890 to 24990 ham radio
11 meters 25670 to 26100 kHz broadcasting
10 meters 28000 to 29700 kHz ham radio

You'll notice some inconsistencies in the table above. For example, the 17-meter ham radio band is actually higher in frequency than the 16-meter broadcasting band. These inconsistencies have come about from years of use (misuse?) of a particular "meter band" to refer to a certain range of frequencies.

Modes and Modulation

Modulation is the process by which voice, music, and other "intelligence" is added to the radio waves produced by a transmitter. The different methods of modulating a radio signal are called modes. An unmodulated radio signal is known as a carrier. When you hear "dead air" between songs or announcements on a radio station, you're "hearing" the carrier. While a carrier contains no intelligence, you can tell it is being transmitted because of the way it quiets the background noise on your radio.

The different modes of modulation have their advantages and disadvantages. Here is a summary:

Continuous Wave (CW)

CW is the simplest form of modulation. The output of the transmitter is switched on and off, typically to form the characters of the Morse code.

CW transmitters are simple and inexpensive, and the transmitted CW signal doesn't occupy much frequency space (usually less than 500 Hz). However, the CW signals will be difficult to hear on a normal receiver; you'll just hear the faint quieting of the background noise as the CW signals are transmitted. To overcome this problem, shortwave and ham radio receivers include a beat frequency oscillator (BFO) circuit. The BFO circuit produces an internally-generated second carrier that "beats" against the received CW signal, producing a tone that turns on and off in step with the received CW signal. This is how Morse code signals are received on shortwave.

Amplitude Modulation (AM)

Amplitude Modulation

In amplitude modulation, the strength (amplitude) of the carrier from a transmitter is varied according to how a modulating signal varies.

When you speak into the microphone of an AM transmitter, the microphone converts your voice into a varying voltage. This voltage is amplified and then used to vary the strength of the transmitter's output. Amplitude modulation adds power to the carrier, with the amount added depending on the strength of the modulating voltage. Amplitude modulation results in three separate frequencies being transmitted: the original carrier frequency, a lower sideband (LSB) below the carrier frequency, and an upper sideband (USB) above the carrier frequency. The sidebands are "mirror images" of each other and contain the same intelligence. When an AM signal is received, these frequencies are combined to produce the sounds you hear.

Each sideband occupies as much frequency space as the highest audio frequency being transmitted. If the highest audio frequency being transmitted is 5 kHz, then the total frequency space occupied by an AM signal will be 10 kHz (the carrier occupies negligible frequency space).

AM has the advantages of being easy to produce in a transmitter and AM receivers are simple in design. Its main disadvantage is its inefficiency. About two-thirds of an AM signal's power is concentrated in the carrier, which contains no intelligence. One-third of the power is in the sidebands, which contain the signal's intelligence. Since the sidebands contain the same intelligence, however, one is essentially "wasted." Of the total power output of an AM transmitter, only about one-sixth is actually productive, useful output!

Other disadvantages of AM include the relatively wide amount of frequency space an AM signal occupies and its susceptibility to static and other forms of electrical noise. Despite this, AM is simple to tune on ordinary receivers, and that is why it is used for almost all shortwave broadcasting.

High Level (Plate) Amplitude Modulation 

The low level generation of AM (DSB + Carrier) and the progressive amplification of that RF signal with  the final stage being a Linear RF amplifier--Class AB.

In the case of the low level modulation approach, one could use either a 2 quadrant or 4 quadrant multiplier as the modulator.

The difference being: with the 2 quadrant multiplier, negative modulation of greater than 100% causes severe distortion as well as interference on adjacent bands. This is due to the carrier being cut off when the 2 quadrant multiplier cannot furnish any output for negative values of the modulating signals, hence the RF output becomes a pulsed spectrum.
If, however, a 4 quadrant multiplier is used, negative modulation starts to appear as a double sideband suppressed carrier--or in this case, reduced carrier.
The second method is the progressive amplification of only the Carrier Wave with the output stage being, a more efficient, Class C (non-linear) RF amplifier; the modulation is introduced as a very high level audio signal at the final stage --more precisely, the positive plate supply of the RF "Final" Amplifier is made to vary as the modulation audio input signal. 

The High Level modulation cannot handle negative modulation of greater than 100%. As with the 2 quadrant multiplier in the first approach, the carrier is cut off during negative peaks that exceed 100% negative modulation. 

Most commercial AM and FM transmitter output stages--called "Finals"--use Class "C" amplifiers. 

Other transmitters, like Television (visual), SSB, etc., use "Linear Amplifiers," Class AB1 or AB2, which are a combination of Class A and Class B (both being much less efficient than the Class C amplifier).  

Overmodulation as seen at the Receiver

Single Sideband (SSB

Single Sideband Modulation

Since so much power is wasted in AM, radio engineers devised a method to transmit just one sideband and put all of the transmitter's power into sending useful intelligence. This method is known as single sideband (SSB). In SSB transmitters, the carrier and one sideband are removed before the signal is amplified. Either the upper sideband (USB) or lower sideband (LSB) of the original AM signal can be transmitted.

SSB is a much more efficient mode than AM since all of the transmitter's power goes into transmitting useful intelligence. A SSB signal also occupies only about half the frequency space of a comparable AM signal. However, SSB transmitters and receivers are far more complicated than those for AM. In fact, a SSB signal cannot be received intelligibly on an AM receiver; the SSB signal will have a badly distorted "Donald Duck" sound. This is because the carrier of an AM signal does play a major role in demodulating (that is, recovering the transmitted audio) the sidebands of an AM signal. To successfully demodulate a SSB signal, you need a "substitute carrier."

A substitute carrier can be supplied by the beat frequency oscillator (BFO) circuit used when receiving CW signals. However, this means that a SSB signal must be carefully tuned to precise "beat" it against the replacement carrier from the BFO. For best performance, a SSB receiver needs more precise tuning and stability than an AM receiver, and it must be tuned more carefully than an AM receiver. Even when precisely tuned, the audio quality of a SSB signal is less than that of an AM signal.

SSB is used mainly by ham radio operators, military services, maritime and aeronautical radio services, and other situations where skilled operators and quality receiving equipment are common. There have been a few experiments in using SSB for shortwave broadcasting, but AM remains the preferred mode for broadcasting because of its simplicity.

Single Sideband Suppressed Carrier (SSB-SC) modulation was the basis for all long distance telephone communications up until the last decade. It was called "L carrier." It consisted of groups of telephone conversations modulated on upper and/or lower sidebands of contiguous suppressed carriers. The groupings and sideband orientations (USB, LSB) supported hundreds and thousands of individual telephone conversations. 

Due to the nature of-SSB, in order to properly recover the fidelity of the original audio, a pilot carrier was distributed to all locations (from a single very stable frequency source), such that, the phase relationship of the demodulated (product detection) audio to the original modulated audio was maintained.  

Also, SSB was used by the U.S. Air force's Strategic Air Command (SAC) to insure reliable communications between their nuclear bombers and NORAD. In fact, before satellite communications SSB-was the only reliable form of communications with the bombers. 

The main reason-SSB-is superior to-AM,-and most other forms of modulation, is due to the following:

(1) Since the carrier is not transmitted, there is a reduction by 50%  
      of the transmitted power (-3dBm).   --In AM @100% modulation: 1/2 of the power is comprised of the carrier; with the remaining (1/2) power in both sidebands. 

(2) Because in SSB, only one sideband is transmitted, there is a further reduction  
      by 50% in transmitted power (-3dBm (+) -3dBm = -6dBm). 

(3) Finally, because only one sideband is received, the receiver's needed  
      bandwidth is reduced by one half--thus effectively reducing the  
      required power by the transmitter another 50% (-3dBm (+) -3dBm (+) -3dBm = -9dBm).  --Remember, if a receiver's bandwidth can be reduced by 50%: the needed transmitter power is also reduced by 50%, i.e., the receiver's Signal to Noise Ratio (SNR) is improved as the receiver bandwidth is reduced. This of course implies that the signal containing the information is not lost--which is the case in this instance

Frequency Modulation (FM)

Slope Detection

Over Modulation

Single Sideband Modulation

In CW, AM, and SSB, the carrier of the signal will not change in a normally operating transmitter. However, it is possible to modulate a signal by changing its frequency in accordance with a modulating signal. This is the idea behind frequency modulation (FM).

The unmodulated frequency of a FM signal is called its center frequency. When a modulating signal is applied, the FM transmitter's frequency will swing above and below the center frequency according to the modulating signal. The amount of "swing" in the transmitter's frequency in any direction above or below the center frequency is called its deviation. The total frequency space occupied by a FM signal is twice its deviation.

As you might suspect, FM signals occupy a great deal of frequency space. The deviation of a FM broadcast station is 75 kHz, for a total frequency space of 150 kHz. Most other users of FM (police and fire departments, business radio services, etc.) use a deviation of 5 kHz, for a total frequency space occupied of 10 kHz. For these reasons, FM is mainly used on frequency above 30 MHz, where adequate frequency space is available. This is why most scanner radios can only receive FM signals, since most signals found above 30 MHz are FM.

The big advantage of FM is its audio quality and immunity to noise. Most forms of static and electrical noise are naturally AM, and a FM receiver will not respond to AM signals. FM receivers also exhibit a characteristic known as the capture effect. If two or more FM signals are on the same frequency, the FM receiver will respond to the strongest of the signals and ignore the rest. The audio quality of a FM signal increases as its deviation increases, which is why FM broadcast stations use such large deviation. The main disadvantage of FM is the amount of frequency space a signal requires.

Frequency-Shift Keying (FSK)

Like FM, frequency-shift keying (FSK) shifts the carrier frequency of the transmitter. Unlike FM, however, FSK shifts the frequency between just two separate, fixed points. The higher frequency is called the mark frequency while the lower of the two frequencies is called thespace frequency. (By contrast, an FM signal can swing to any frequency within its deviation range.)

FSK was originally developed to send text via radioteleprinter devices, like those used by the TeleType Corporation. The shifting of the carrier between the mark and space was used to generate characters in the Baudot code, which can be thought of as a more elaborate version of the Morse code. At the receiver, the Baudot signals were used to produce printed text on printers and, later, video screens.

As technology improved, FSK was used to transmit messages in the ASCII code used by computers; this permitted the use of upper and lower case letters and special symbols. The introduction of microprocessors made it possible to use FSK to send messages with automatic error detection and correction capabilities. This is done by including error checking codes into messages and allowing the receiving station to request a retransmission of a message if the message and its error checking code are in conflict (or if the code is not received.) Among the most common such FSK modes are amateur teleprinting over radio (AMTOR) and forward error correction (FEC).

FSK is the fastest way to send text by radio, and the error-correcting modes offer high accuracy and reliability. The frequency space occupied depends on the amount of shifting, but typical FSK signals occupy less than 1.5 kHz of space. The big disadvantage of FSK is the more elaborate receiving gear required.

Special receiving terminals and adapters are available to let you "see" FSK modes. Many of these work in conjunction with personal computers.

Digital Modes

The same technology that makes it possible for you to view this Web site is also being used on the air. Digital modes can organize information into packets that contain address fields, information about the transmission protocol being used, error detection code, a few hundred bytes of data, and bits to indicate where each packet begins and ends.

Instead of transmitting messages in continuous streams, packet modes break them into packets. At the receiving end, the different packets are re-assembled to form the original message. If a packet is missing or received with errors, the receiving station can request a retransmission of the packet. Packets can be received out of sequence or even from multiple sources (such as different relaying stations) and still be assembled into the original message by the receiving station.

While packet modes have mainly been used to send text, any information that can be converted into digital form---sound, graphics, video, etc.---can be transmitted by digital modes.

Another advantage of packet modes is that packets can be addressed to specific stations in the address field of each packet. Other stations will ignore packets not addressed to them.

The big disadvantage of packet modes is the complexity of the necessary receiving and transmitting gear. The frequency space occupied is directly proportional to the speed at which messages are transmitted, and radio digital modes are very slow compared to their Internet equivalents. The slowest Web connection via the Internet is 14,400 baud (14.4K), while the maximum practical digital mode rate via radio is 9600 baud (9.6K). On frequencies below 30 MHz, it is even slower; rates are usually restricted to just 300 baud (0.3K)! As a result, digital modes via radio today deliver performance far short of their potential.

Special receiving adapters for packet modes are available, and these usually work in conjunction with personal computers. Most offer FSK receiving capabilities as well.

Another form of digital modulation is known as spread spectrum. Most other modulation methods pack all of the transmitter's output power into a bandwidth of only a few kHz. (Even in FM, the carrier doesn't occupy much bandwidth, although its frequency may be deviated over a wide range.) Spread spectrum literally "spreads" the carrier over a frequency range that may be as much as 10 kHz on frequencies below 30 MHz. (Spreading over 100 kHz or more is common on the VHF and UHF bands.) This spreading is usually done via a "spreading code" contained in an internal microcontroller chip.

When heard on a conventional receiver, spread sprectrum sounds like random noise or "gurgling" water. A receiver equipped with a microcontroller having the matching "spreading code" is necessary to properly receive the spread spectrum transmission. Advantages of spread spectrum include a high degree of privacy and freedom from intereference, since the spread spectrum receiver will reject any signal not having the proper spreading code. Almost all users of spread spectrum below 30 MHz are various military and government services.


Communication technologies that are specifically designed to improve "live" HF keyboard operation can now be achieved which were previously only theory, too complex, or too costly to implement to be practical. Thanks to the generosity of radio amateurs (hams) with programming knowledge, and to the Internet, new and powerful communications tools are available to all hams. The evolution and wide spread use of the Personal Computer that include a digital sound card for Digital Signal Processing (DSP), is allowing radio amateurs to use these tools to develop new modes of digital communication. The distinguishing features of live HF digital operation today are the use of lower power, compact or indoor antennas and courteous operating techniques. This reverses the trend of several years ago.

Confusion over band space is the obvious down-side as new and old modes compete for space on the HF bands. Crowding on a single band like 20 meters is partly to blame for this issue. Fortunately, the new modes like MFSK16, are designed to improve performance for a wide range of operating conditions. This should allow for increased amateur radio band usage to relieve crowding and extend contact opportunities as propagation changes to favor different bands. These are really exciting times for all radio amateurs the use and enjoy all these new digital modes! 

An Overview of Digital HF Radio Operating Modes

TOR is an acronym for Teleprinting Over Radio. It is traditionally used to describe the three popular "error free" communication modes - AMTOR, PACTOR and G-TOR. The main method for error correction is from a technique called ARQ (Automatic Repeat Request) which is sent by the receiving station to verify any missed data. Since they share the same method of transmission (FSK), they can be economically provided together in one Terminal Node Controller (TNC) radio modem and easily operated with any modern radio transceiver. TOR methods that do not use the ARQ hand-shake can be easily operated with readily available software programs for personal computers. For the new and less complex digital modes, the TNC is replaced by an on-board sound card in the personal computer. 

AMTOR is an FSK mode that is hardly used by radio amateurs in the 21st Century. While a robust mode, it only has 5 bits (as did its predecessor RTTY) and can not transfer extended ASCII or any binary data. With a set operating rate of 100 baud, it does not effectively compete with the speed and error correction of more modern ARQ modes like Pactor. The non-ARQ version of this mode is known as FEC, and known as SITOR-B by the Marine Information services.

To hear what an Amtor signal sounds like, click the icon sound icon

PACTOR is an FSK mode and is a standard on modern Multi-Mode TNCs. It is designed with a combination of packet and Amtor Techniques. Although this mode is also fading in use, it is the most popular ARQ digital mode on amateur HF today and primarily used by amateurs for sending and receiving email over the radio. This mode is a major advancement over AMTOR, with its 200 baud operating rate, Huffman compression technique and true binary data transfer capability.

To hear what a Pactor signal sounds like, click the icon sound icon 

G-TOR (Golay -TOR) is an FSK mode that offers a fast transfer rate compared to Pactor. It incorporates a data inter-leaving system that assists in minimizing the effects of atmospheric noise and has the ability to fix garbled data. G-TOR tries to perform all transmissions at 300 baud but drops to 200 baud if difficulties are encountered and finally to 100 baud. (The protocol that brought back those good photos of Saturn and Jupiter from the Voyager space shots was devised by M.Golay and now adapted for ham radio use.) GTOR is a proprietary mode developed by Kantronics. Because it is only available with Kantronics multi-mode TNCs, it has never gained in popularity and is rarely used by radio amateurs.

To hear what a G-TOR signal sounds like, click the icon sound icon 

PACTOR II is a robust and powerful PSK mode which operates well under varying conditions. It uses strong logic, automatic frequency tracking; it is DSP based and as much as 8 times faster then Pactor. Both PACTOR and PACTOR-2 use the same protocol handshake, making the modes compatible. As with the original Pactor, it is rarely used by radio amateurs since the development of the new PC based sound card modes. Also, like GTOR, it is a proprietary mode owned by SCS and only available with their line of multi-mode TNC controllers.

To hear what a PactorII signal sounds like, click the icon sound icon 

CLOVER is a PSK mode which provides a full duplex simulation. It is well suited for HF operation (especially under good conditions), however, there are differences between CLOVER modems. The original modem was named CLOVER-I, the latest DSP based modem is named CLOVER-II. Clovers key characteristics are band-width efficiency with high error-corrected data rates. Clover adapts to conditions by constantly monitoring the received signal. Based on this monitoring, Clover determines the best modulation scheme to use.

To hear what a Clover signal sounds like, click the icon sound icon 

RTTY or "Radio Teletype" is a FSK mode that has been in use longer than any other digital mode (except for morse code). RTTY is a very simple technique which uses a five-bit code to represent all the letters of the alphabet, the numbers, some punctuation and some control characters. At 45 baud (typically) each bit is 1/45.45 seconds long, or 22 ms and corresponds to a typing speed of 60 WPM. There is no error correction provided in RTTY; noise and interference can have a seriously detrimental effect. Despite it's relative disadvantages, RTTY is still popular with many radio amateurs. This mode has now been implemented with commonly available PC sound card software.

To hear what a RTTY signal sounds like, click the icon sound icon 

PSK31 is the first new digital mode to find popularity on HF bands in many years. It combines the advantages of a simple variable length text code with a narrow bandwidth phase-shift keying (PSK) signal using DSP techniques. This mode is designed for "real time" keyboard operation and at a 31 baud rate is only fast enough to keep up with the typical amateur typist. PSK31 enjoys great popularity on the HF bands today and is presently the standard for live keyboard communications. Most of the ASCII characters are supported. A second version having four (quad) phase shifts (QPSK) is available that provides Forward Error Correction (FEC) at the cost of reduced Signal to Noise ratio. Since PSK31 was one of the first new digital sound card modes to be developed and introduced, there are numerous programs available that support this mode - most of the programs available as "freeware".

To hear what a PSK31 signal sounds like, click the icon sound icon 

HF PACKET (300 baud) radio is a FSK mode that is an adaption of the very popular Packet radio used on VHF (1200 baud) FM amateur radio. Although the HF version of Packet Radio has a much reduced bandwidth due to the noise levels associated with HF operation, it maintains the same protocols and ability to "node" many stations on one frequency. Even with the reduced bandwidth (300 baud rate), this mode is unreliable for general HF ham communications and is mainly used to pass routine traffic and data between areas where VHF repeaters maybe lacking. HF and VHF Packet has recently enjoyed a resurgence in popularity since it is the protocol used by APRS - Automatic Position Reporting System mostly on 2 meter VHF and 30 meter HF.

To hear what a packet signal sounds like, click the icon sound icon 

HELLSCHREIBER is a method of sending and receiving text using facsimile technology. This mode has been around along time. It was actually developed by Germany prior to World War II! The recent use of PC sound cards as DSP units has increased the interest in Hellschreiber and many programs now support this new...well I mean, old mode. The single-tone version (Feld-Hell) is the method of choice for HF operation. It is an on-off keyed system with 122.5 dots/second, or about a 35 WPM text rate, with a narrow bandwidth (about 75 Hz). Text characters are "painted" on the screen, as apposed to being decoded and printed. Thus, many different fonts can be used for this mode including some basic graphic characters. A new "designer" flavor of this mode called PSK HELL has some advantage for weak signal conditions. As with other "fuzzy modes" it has the advantage of using the "human processor" for error correction; making it the best overall mode for live HF keyboard communications. Feld-Hell also has the advantage of having a low duty cycle meaning your transmitter will run much cooler with this mode.

To hear what a Hellschreiber signal sounds like, click the icon sound icon 

MT63 is a new DSP based mode for sending keyboard text over paths that experience fading and interference from other signals. It is accomplished by a complex scheme to encode text in a matrix of 64 tones over time and frequency. This overkill method provides a "cushion" of error correction at the receiving end while still providing a 100 WPM rate. The wide bandwidth (1Khz for the standard method) makes this mode less desirable on crowded ham bands such as 20 meters. A fast PC (166 Mhz or faster) is needed to use all functions of this mode. MT63 is not commonly used by amateurs because of its large bandwidth requirement and the difficulty in tuning in an MT63 transmission.

To hear what a MT63 signal sounds like, click the icon sound icon 

THROB is yet another new DSP sound card mode that attempts to use Fast Fourier Transform technology (as used by waterfall displays). THROB is actually based on tone pairs with several characters represented by single tones. It is defined as a "2 of 8 +1 tone" system, or more simply put, it is based on the decode of tone pairs from a palette of 9 tones. The THROB program is an attempt to push DSP into the area where other methods fail because of sensitivity or propagation difficulties and at the same time work at a reasonable speed. The text speed is slower than other modes but the author (G3PPT) has been improving his MFSK (Multiple Frequency Shift Keying) program. Check his web site for the latest developments.

To hear what a Throb signal sounds like, click the icon sound icon 

MFSK16 is an advancement to the THROB mode and encodes 16 tones. The PC sound card for DSP uses Fast Fourier Transform technology to decode the ASCII characters, and Constant Phase Frequency Shift Keying to send the coded signal. Continuous Forward Error Correction (FEC) sends all data twice with an interleaving technique to reduce errors from impulse noise and static crashes. A new improved Varicode is used to increase the efficiency of sending extended ASCII characters, making it possible to transfer short data files between stations under fair to good conditions. The relatively wide bandwidth (316 Hz) for this mode allows faster baud rates (typing is about 42 WPM) and greater immunity to multi path phase shift. A second version called MFSK8 is available with a lower baud rate (8) but greater reliability for DXing when polar phase shift is a major problem. Both versions are available in a nice freeware Windows program created by IZ8BLY.

To hear what an MFSK16 signal sounds like, click the icon sound icon 

Double SideBand Modulation

Single Sideband Modulation

Double SideBand Suppressed Carrier (DSB-SC)


Quadrature Amplitude Modulation  (QAM)

Single Sideband Modulation

I & Q modulation, A.K.A., QAM, is a method for sending two separate (and uniquely different) channels of information. 

As you know, the carrier is shifted to create two carriers: sin and cos versions. 

The two modulation inputs (analog or digital) are applied to two separate balanced modulators (BM) each of which are supplied  with the sin or cos carriers, i.e., modulator #1 is supplied with the sin carrier and modulator #2 is supplied with the cos carrier. 

The outputs of both modulators are algebraically summed; the result of which is now a single signal to be transmitted,  containing the I & Q information. 

This signal is for all intents and purposes a 'Double Sideband Signal' (DSB) with or without a carrier (reduced). 

In the case of color television chroma, the subcarrier is transmitted as a very short burst (8 to 9 alternations); the reconstituted  carrier is derived from this burst at the receiver. 

This method of modulation has the advantage of reducing or eliminating intermodulation interference caused by a continuous  carrier near the modulation sidebands. 

Upon reception, the composite signal ( I & Q) is processed to extract a carrier replica which is again shifted in phase to create  both sin and cos carriers. 

These carriers are applied to two different demodulators; each demodulator outputs one of the two original signals applied in the  modulation process (I & Q) at the transmitter. 

In the more recent incarnations of the QAM or I & Q modulation techniques, an Analog to Digital Convertor (ADC) is used to  first convert the analog input to a serialized digital bit stream and is applied to the QAM modulators; likewise at the receiver. 


Call Sign Prefixes

Most radio stations are issued a call sign (also known as call letters) by the government that licenses or authorizes them. Call signs consist of a one or two letter/numeral prefix, a numeral, and an alphabetical suffix.

The different nations that authorize or license radio stations are assigned, by international agreement, a set of unique call sign prefixes to help identify where a station is located and under which national authority the station is operating. As a result, these prefixes can be a big aid in determining where a station you're hearing is located.

Call sign prefixes are not an infallible way to determine a station's location, however. A shipboard station will use the call letters assigned to it by its home nation regardless of where it is operating from. A nation's call sign allocations are also used for its territories and possessions, no matter how remote from the nation (for example, call signs in Guam use the U.S. allocations despite being distant from the landmass of the United States). Some stations in the former Soviet Union use their "traditional" call signs despite being located in a now-independent republic with different allocations. Many military stations use "tactical" call signs that follow no set allocations or rules. However, most ham radio, broadcasting, and maritime stations will have their call signs assigned in accordance with the list on this page.

Many call signs will not use all three characters of a prefix. For example, AA9XXX and AAA9XXX would both be valid call signs for a station licensed by the United States.

Note that no official call signs use the QAA-QZZ block. These are reserved for international radiotelegraph "Q-signals." The most common Q-signals are found in our Radio Terms section.

The allocations in the following list are in alphanumeric order. Click the letters in the table below to go to the allocation(s) beginning with the indicated letter(s) or number(s). To return to the table, click Top at the end of each allocation segment.

CQA-CUZ: Portugal

UTC/GMT Conversion

Since radio signals can cross multiple time zones and the international date line, some worldwide standard for time and date is needed. This standard is coordinated universal time, abbreviated UTC. This was formerly known as Greenwich mean time (GMT). Other terms used to refer to it include "Zulu time" (after the "Z" often used after UTC times), "universal time," and "world time."

UTC is used by international shortwave broadcasters in their broadcast and program schedules. Ham radio operators, shortwave listeners, the military, and utility radio services are also big users of UTC. All of the times and dates found here at at UTC unless otherwise indicated.

Greenwich mean time was based upon the time at the zero degree meridian that crossed through Greenwich, England. GMT became a world time and date standard because it was used by Britain's Royal Navy and merchant fleet during the nineteenth century. Today, UTC uses precise atomic clocks, shortwave time signals, and satellites to ensure that UTC remains a reliable, accurate standard for scientific and navigational purposes. Despite the improvements in accuracy, however, the same principles used in GMT have been carried over into UTC.

UTC uses a 24-hour system of time notation. "1:00 a.m." in UTC is expressed as 0100, pronounced "zero one hundred." Fifteen minutes after 0100 is expressed as 0115; thirty-eight minutes after 0100 is 0138 (usually pronounced "zero one thirty-eight"). The time one minute after 0159 is 0200. The time one minute after 1259 is 1300 (pronounced "thirteen hundred"). This continues until 2359. One minute later is 0000 ("zero hundred"), and the start of a new UTC day.

To convert UTC to local time, you have to add or subtract hours from it. For persons west of the zero meridian to the international date line (which includes all of North America), hours are subtracted from UTC to convert to local time. Below is a table showing the number of hours to subtract from local time zones in North America in order to convert UTC to local time:

The second table is direct conversion from UTC to U.S.A. timezones.

0000 8 PM 7 PM 6 PM 5 PM 4 PM
0100 9 PM 8 PM 7 PM 6 PM 5 PM
0200 10 PM 9 PM 8 PM 7 PM 6 PM
0300 11 PM 10 PM 9 PM 8 PM 7 PM
0400 Midnight 11 PM 10 PM 9 PM 8 PM
0500 1 AM Midnight 11 PM 10 PM 9 PM
0600 2 AM 1 AM Midnight 11 PM 10 PM
0700 3 AM 2 AM 1 AM Midnight 11 PM
0800 4 AM 3 AM 2 AM 1 AM Midnight
0900 5 AM 4 AM 3 AM 2 AM 1 AM
1000 6 AM 5 AM 4 AM 3 AM 2 AM
1100 7 AM 6 AM 5 AM 4 AM 3 AM
1200 8 AM 7 AM 6 AM 5 AM 4 AM
1300 9 AM 8 AM 7 AM 6 AM 5 AM
1400 10 AM 9 AM 8 AM 7 AM 6 AM
1500 11 AM 10 AM 9 AM 8 AM 7 AM
1600 Noon 11 AM 10 AM 9 AM 8 AM
1700 1 PM Noon 11 AM 10 AM 9 AM
1800 2 PM 1 PM Noon 11 AM 10 AM
1900 3 PM 2 PM 1 PM Noon 11 AM
2000 4 PM 3 PM 2 PM 1 PM Noon
2100 5 PM 4 PM 3 PM 2 PM 1 PM
2200 6 PM 5 PM 4 PM 3 PM 2 PM
2300 7 PM 6 PM 5 PM 4 PM 3 PM

A major source of confusion when using UTC is that the date also follows UTC. Suppose your local time zone is Central standard, and you want to hear a shortwave program scheduled to be broadcast at 0400 UTC Saturday. You do the math, and find that 0400 UTC is equal to 10:00 p.m. Central standard time. If you tune in at 10:00 p.m. on Saturday, however, you won't hear the program. Since the date is also UTC, you need to listen at 10:00 p.m. Friday to hear the program.

To hear the latest time in UTC, you can tune to stations WWV, in Fort Collins, Colorado and WWVH, Kauai, Hawaii on 2500, 5000, 10000 and 15000 kHz to hear the time announced in UTC each minute. WWV uses a man's voice to give the time, while WWVH uses a female voice. If you live in the central or eastern United States, and those frequencies aren't usable, you can tune to station CHU, in Ottawa, Ontario, Canada on 3330, 7335 7850 and 14670 kHz, to hear the current UTC time. If you're like many radio hobbyists, you will soon add a second clock set to UTC to your collection of radio gear. Click here for information on 24 hour clocks

Radio Terms and Abbreviations

The nomenclature of the radio hobby can be bewildering! The following is a list of some of the more widely used (and confused!) terms and abbreviations found in ham radio, shortwave radio, and scanner monitoring.

Click below on the first letter in the term you wish to have defined, and you will go to the start of the terms beginning with that letter. The "digits" selection are terms that are numbers. You can return to the top of this page by clicking Top at the end of each section of definitions. If a definition contains an italicized phrase, that phrase is also defined on this page.


Introduction to Shortwave Listening

Shortwave listening (abbreviated SWLing) is tuning for stations located on shortwave frequencies, usually thought of as those from 1700 kHz (the upper limit of the AM broadcasting band) to 30 MHz (the lower limit of the tuning range of most scanner radio). In between those two frequencies, a simple, low cost shortwave radio is capable of letting you hear news, music, commentaries, and other feature programs in English from stations located round the world.

Most of the larger nations of the world broadcast programs in English especially for North American audiences, and transmit them on times and frequencies for best reception in North America.

But why bother listening to shortwave in this era of communications satellites and cable television news channels? Perhaps the biggest reason why is that SWLing can give you a unique perspective on events that you simply cannot get from American media. If you watch coverage of an event in Moscow from CCN or CBS News, you get the American perspective on what is happening from an American journalist. If you listen to the Voice of Russia, you get the Russian perspective from a Russian journalist. As you might expect, the two interpretations of the same news event can be quite different.

Ever heard a country be reborn? Listeners to Germany's Deutsche Welle on October 3, 1990 heard live coverage of the reunification ceremonies and received this souvenir QSL card for their reception reports.

Shortwave also lets you get foreign reactions to and interpretations of American news events. For example, in 1992 I was fascinated at how other nations attempted to understand the presidential candidacy of H. Ross Perot. Even European democracies like Britain and Germany seemed bewildered by his candidacy and popularity; they could not understand how someone could declare himself a presidential candidate and achieve such popularity outside of a political party system. Moments like that help you appreciate the profound cultural and intellectual differences that exist between ostensibly closely-linked nations.

While no one knows the exact number of shortwave listeners (SWLs) in the United States, most estimates place the number in the millions. SWLs range from teenagers to retired persons to David Letterman, who has mentioned on several occasions how much he enjoys listening to shortwave, particularly broadcasts by the British Broadcasting Corporation (BBC).

Of course, not all shortwave stations broadcast in English. If you’re studying a foreign language—or want to maintain your proficiency in one—shortwave radio will offer you an unlimited supply of contemporary practice material. If you enjoy music, shortwave will let you hear sounds you probably can’t find in the even the most specialized record and CD shops. Ever heard a lagu melayu song? It sounds like a cross between Indian-style instrumentals and an Arabic vocal style, and it’s very popular in Indonesia. You can hear such songs over the various shortwave outlets of Radio Republic Indonesia. The so-called "world beat" popular with young people had its origins in the "high life" music broadcast by shortwave stations in Africa. Other SWLs arise before dawn to catch the haunting huayno melodies coming from stations in Bolivia and Peru. Some SWL music fans have compiled tape-recorded libraries of folk and indigenous music from shortwave broadcasts that many college and university music departments would envy!

Most stations operating on shortwave frequencies are not broadcasters, however. Ham radio operators have certain frequency bands set aside for their use, and you can hear them "talking" (by voice, Morse code, radioteletype, etc.) with friends around the world. Aircraft flying international routes, ships at sea, and military forces are also big users of shortwave. In fact, some SWLs ignore broadcasters altogether and specialize in trying to hear such "utility" stations.

Another specialty within SWLing is "DXing," in which the goal is to receive faint, distant, and otherwise hard-to-hear stations. DXing on shortwave is like panning for gold; DXers patiently work through noise, interference, and fading to hear a low powered station deep in the Amazonian basin of Brazil or somewhere in the Indonesian archipelago.

DXing is a manifestation of shortwave’s biggest weakness—the fact that shortwave reception is highly variable compared to the AM and FM broadcasting bands. Reception of a shortwave station on a given frequency will usually vary greatly with the time of day and season of the year. Shortwave reception is heavily influenced by solar activity as indicated by the number of sunspots visible on the Sun. Solar flares and storms can disrupt shortwave reception for hours and even days. Fading is also common on the shortwave bands. While shortwave can offer you listening you cannot find on your local AM and FM stations, it unfortunately cannot offer you the same reliable reception or audio quality.

Many shortwave stations welcome correspondence from listeners, especially reports on how well the station is being received and comments on their programming. Stations often respond to such letters by sending out colorful souvenir cards, known as QSL cards, for correct reports of reception. Some station reply with QSL letters instead of cards, and a few send other items, like pennants with the station’s name or call letters, to lucky SWLs.

A blast from the past! Colombia's Radio Mira sent out this pennant in 1974 to mark their "new image." For years, the parrot was the symbol of Colombia's TODELAR broadcasting network.

It is difficult to imagine anyone interested in what’s happening beyond the borders of their home nation not owning a shortwave radio. No other tool can provide you with such a wide array of news, music, and culture for such modest investment. Even in this age of satellite television and the Web, there are significant portions of the world that can only be accessed via shortwave radio. The whole world is talking on shortwave radio. Why not give a listen?

Tuning 150 kHz to 30 MHz

Most "shortwave" radios sold today actually tune a much broader frequency range that includes the AM broadcast band and parts of the longwave spectrum. A typical tuning range is from about 150 kHz to 30 MHz.

By international agreement, the radio spectrum has been divided up among various users. While there are some exceptions, most nations and the stations they authorize do follow the allocations described below:

150 kHz and below: Signals on these frequencies cannot propagate well via the ionosphere, but are able to penetrate ocean water well. As a result, several military stations used for submarine communications are found here. Most transmissions are in CW and RTTY. You need a really large antenna to hear much here, and in most locations electrical noise and static will be too high.

150 to 540 kHz: This is what most SWLs mean by "longwave." Most stations heard in this range are navigation beacons that continuously repeat their call signs in Morse code. There is a also a broadcasting band in Europe from 155 to 281 kHz. Some RTTY signals are found in the upper end of this band. Marine weather and safety broadcasts, known as NAVTEX, are transmitted on 512 kHz. Your best reception here will be at night, especially during the fall and winter months.

540 to 1700 kHz: This is the AM broadcasting or "medium wave" band which use to end at 1600 kHz. The AM broadcast band now ends at 1700 kHz, with 1610 to 1700 kHz being the new "X" or "extended" band. New stations began appearing here in late 1997, and this new "X band" is providing excellent DX listening opportunities.

1700 to 1800 kHz: This is a "grab bag" of miscellaneous radio communications, mainly beacons and navigation aids. You may hear several transmitters that sound like chirping crickets; these are floating beacons used to mark fishing and offshore oil exploration locations.

1800 to 2000 kHz: This is the 160-meter ham radio band. Most voice communications will be in LSB, with best reception at night during the fall and winter months.

2000 to 2300 kHz: This range is used maritime communications, with 2182 kHz reserved for distress messages and calling. There are also several regularly scheduled maritime weather broadcasts buy U.S. Coast Guard stations. Most activity will be in USB, and best reception is at night.

2300 to 2498 kHz: This is the 120-meter broadcasting band, mainly used by stations located in the tropics. However, the FCC has allowed WWCR in Nashville, Tennessee to broadcast here and others may follow.

2498 to 2850 kHz: More maritime stations are found here, as well as standard time and frequency stations WWV and WWVH on 2500 kHz.

2850 to 3150 kHz: This band is used mainly by aeronautical stations in USB. Several stations broadcasting aeronautical weather bulletins, and you can also hear traffic between airports and airplanes aloft.

3150 to 3200 kHz: This range is allocated to fixed stations, with most communications in RTTY.

3200 to 3400 kHz: This is a very interesting segment. This us the 90-meter broadcasting band, used mainly by stations in the tropics. Canadian standard time and frequency station CHU can be heard on 3330 kHz. Several fixed stations also use this range, including several associated with various agencies of the U.S. government. Best reception will be at night.

3400 to 3500 kHz: This range is used for aeronautical communications in USB.

3500 to 4000 kHz: This is the 80-meter ham radio band. The 3500 to 3750 kHz range is used for CW and RTTY communications, and the rest of the band is used for LSB voice. The 3900 to 4000 kHz range is used for broadcasting in Europe and Africa. Best reception is at night.

4000 to 4063 kHz: This is a fixed station band, mainly used by military forces for SSB traffic.

4063 to 4438 kHz: This is a band used for maritime communications in USB, with 4125 kHz being used as a calling frequency.

4438 to 4650 kHz: This range is mainly used for fixed and mobile stations in USB.

4750 to 4995 kHz: This is the 60-meter broadcasting band, used mainly by stations in the tropics. Best reception is in the evening and night hours during the fall and winter. In winter, stations to the east of you begin to fade in an hour or two before your local sunset, and stations to the west of you don’t start to fade out until an hour or so after your local sunrise.

4995 to 5005 kHz: This range is allocated internationally to standard time and frequency stations. In North America, you’ll mainly hear WWV and WWVH on 5000 kHz.

5005 to 5450 kHz: This range is a real jumble! Several broadcasting stations are found in the lower part of the segment, and fixed and mobile stations in SSB, RTTY, and CW are found throughout this band. Best reception is during the evening and night hours.

5450 to 5730 kHz: This is another band for aeronautical communications in USB.

5730 to 5950 kHz: Another jumble of different stations! For years, this band has been used by fixed stations of the U.S. government for communications in USB and RTTY. However, several broadcasters are also showing up here.

5950 to 6200 kHz: This is the 49-meter broadcasting band, and is loaded with signals from late afternoon to a couple of hours after your local sunrise.

6200 to 6525 kHz: This is a very busy band for maritime communication in USB and various FSK modes like AMTOR and FEC.

6525 to 6765 kHz: This is another busy band, this time for aeronautical communications in USB. Best reception is during the evening and night hours.

6765 to 7000 kHz: This segment is allocated to fixed stations, with signals in SSB, CW, FAX modes, and miscellaneous digital modes.

7000 to 7300 kHz: The 7000 to 7100 kHz range is allocated exclusively to ham radio worldwide, although an occasional broadcaster will show up here. The 7100 to 7300 kHz range is allocated exclusively to ham radio in North and South America, but is used for broadcasting in the rest of the world. Several station transmit programs intended for reception in North and South America in this range. As a result, interference is often very heavy here during the night and evening hours. Hams use CW and RTTY from 7000 to 7150 kHz, and mainly LSB from 7150 to 7300 kHz. Best reception is from the late afternoon to early morning, although some hams can usually be heard here around the clock.

7300 to 8195 kHz: This segment is mainly used by fixed stations, such as Canadian standard time and frequency station CHU on 7335 7850 kHz, although several broadcasters can be found in the lower reaches. Various FSK (RTTY) and digital modes are used.

8195 to 8815 kHz: This is a busy maritime band from the late afternoon until early morning, with most traffic in USB and FSK modes.

8815 to 9040 kHz: This is another aeronautical communications band, with traffic in USB. Several stations hear broadcast aeronautical weather reports.

9040 to 9500 kHz: This range is used mainly by fixed station in various FSK and digital modes, but it is also used by several international broadcasters.

9500 to 9900 kHz: This is the 31-meter international broadcasting band, and is packed with stations from around the world. Best reception is usually from mid-afternoon to around mid-morning, although some stations can be heard here throughout the day, especially in winter.

9900 to 9995 kHz: Several international broadcasters use this range along with fixed stations using FSK modes.

9995 to 10005 kHz: This is set aside for standard time and frequency stations, like WWV and WWVH on 10000 kHz.

10005 to 10100 kHz: This range is used for aeronautical communications.

10100 to 10150 kHz: This is the 30-meter ham radio band. Because it is so narrow, operation here is restricted to CW and RTTY.

10150 to 11175 kHz: This segment is used by fixed stations. In addition to various FSK and digital modes, you may hear several international broadcast stations being relayed in SSB. These "feeder" stations are used to send programming to relay sites not served by satellite downlinks.

11175 to 11400 kHz: This range is used for aeronautical communications in USB.

11400 to 11650 kHz: This segment is mainly used by fixed stations in FSK and digital modes, but some international broadcasters also operate here.

11650 to 11975 kHz: This is the 25-meter international broadcasting band. You can usually hear several stations here no matter what time of day you listen.

11975 to 12330 kHz: This band is primarily used by fixed stations in FSK and digital modes, although several international broadcasters are found in the lower area.

12330 to 13200 kHz: This is a busy maritime communications band during the day and evening hours, with traffic in USB and various FSK modes.

13200 to 13360 kHz: Aeronautical communications in USB are heard here during the day and evening.

13360 to 13600 kHz: This range is used by fixed stations, mainly in FSK and digital modes.

13600 to 13800 kHz: This is the 22-meter international broadcasting band, with best reception generally during the daytime and early evening.

13800 to 14000 kHz: This is used by fixed stations, with most communications in FSK modes.

14000 to 14350 kHz: This is the 20-meter ham radio band. The lowest 100 kHz is reserved for CW and RTTY use, with USB popular in the rest of the band (although U.S. hams cannot transmit in SSB below 14150 kHz). Best reception is during the daytime and early evening.

14350 to 14990 kHz: This segment is used by fixed stations, primarily in FSK and digital modes. Canadian standard time station CHU is also found here, on 14670 kHz.

14990 to 15010 kHz: This sliver is reserved for standard time and frequency stations, with the best heard being WWV and WWVH on 15000 kHz.

15010 to 15100 kHz: This range is for aeronautical communications in USB, although a few international broadcasters do show up here.

15100 to 15600 kHz: This is the 19-meter international broadcasting band, and it is usually packed with signals during the daytime and early evening.

15600 to 16460 kHz: This band is used by fixed stations in USB, FSK modes, and digital modes.

16460 to 17360 kHz: This range is shared between maritime and fixed stations using USB, FSK modes, and digital modes. Best reception here is generally during the daytime.

17360 to 17550 kHz: The range is shared by aeronautical and fixed stations using USB, FSK modes, and digital modes.

17550 to 17900 kHz: This is the 16-meter international broadcasting band, and best reception is usually during the daylight hours.

17900 to 18030 kHz: This band is used for aeronautical communications in USB.

18030 to 18068 kHz: This range is used by fixed stations, mainly in FSK and digital modes.

18068 to 18168 kHz: This is the 17-meter ham radio band, where CW, RTTY, and USB are used.

18168 to 19990 kHz: This large band is used by fixed stations, with a few maritime stations also found here. Most traffic is in FSK and digital modes. An interesting frequency is 19954 kHz, used for decades as a beacon frequency by Soviet/Russian manned spacecraft. Reception in this range will usually be limited to daylight hours.

19990 to 20010 kHz: This segment is reserved for standard time and frequency stations, like WWV on 20000 kHz. Reception here is usually possible only in daytime.

20010 to 21000 kHz: This range is mainly used by fixed stations and a few aeronautical stations. Most traffic is in FSK and digital modes as well as USB.

21000 to 21450 kHz: This is the 15-meter ham radio band. CW and RTTY is mainly found in the first 200 kHz, and USB is used in the rest of the band. Best reception here is in the daytime hours.

21450 to 21850 kHz: This is the 13-meter international broadcasting band, with best reception during the daytime.

21850 to 22000 kHz: This band is shared by fixed and aeronautical stations in FSK and digital modes as well as USB.

22000 to 22855 kHz: This range is reserved for maritime communications in USB and FSK modes. Best reception is in daytime during years of high sunspot activity.

22855 to 23200 kHz: This band is used by fixed stations, mainly in FSK and digital modes.

23200 to 23350 kHz: Aeronautical communications in USB are found here.

23350 to 24890 kHz: This segment is used by fixed stations in FSK and digital modes.

24890 to 24990 kHz: This is the 12-meter ham radio band, used for CW, FSK, and USB work. Reception is usually limited to the daytime during years of high sunspot activity.

24990 to 25010 kHz: This range is for standard time and frequency stations, although none are currently operating here.

25010 to 25550 kHz: This band is used by fixed, mobile, and maritime stations, many of them low powered units in trucks, taxicabs, small boats, etc. USB and AM are mainly used, along with FM having 5 kHz deviation. Best reception is during daytime in years of high sunspot activity or during a sporadic-E propagation opening.

25550 to 25670 kHz: This region is reserved for radio astronomy and is usually free of stations.

25670 to 26100 kHz: This is the 11-meter international broadcasting band. However, only Radio France International has any broadcasts scheduled here at this time.. Reception is usually possible only in daytime during years of high sunspot activity.

26100 to 28000 kHz: This band is used by fixed, mobile, and maritime stations, many of them low powered units in trucks, taxicabs, small boats, etc. USB and AM are mainly used, along with FM having 5 kHz deviation. The citizens band (CB) is found from 26965 to 27405 kHz. Best reception is during daytime in years of high sunspot activity or during a sporadic-E propagation opening.

28000 to 29700 kHz: This is the 10-meter ham radio band. Most activity is in USB from 28300 to 28600 kHz, with FM used on 29600 kHz. Best reception is during daytime in years of high sunspot activity or during a sporadic-E propagation opening.

29700 to 30000 kHz: This range is used by low powered fixed and mobile stations, mainly using FM with 5 kHz deviation.

Selecting a Shortwave Radio

There are many different makes and models of shortwave radios, and they vary greatly in cost, features, size, complexity, and other factors. There is no one "right" shortwave radio for everyone. The best shortwave radio for you depends primarily on your listening interests.However, there are some features and specifications you should look for in any shortwave radio you consider. They are:

• Frequency coverage. Shortwave frequencies are usually considered those from the upper end of the AM broadcasting band, 1700 kHz, up to 30 MHz. The minimum frequency coverage you should look for is 540 kHz to 30 MHz. Most shortwave radios sold today also tune down to 150 kHz, covering the longwave band.

• Frequency readout. Most shortwave radios sold today have a digital display showing the frequency the radio is tuned to. A few radios, usually less expensive models, have an analog "slide rule" frequency readout that does not indicate the precise frequency the radio is receiving. It can be very difficult and frustrating to find a station on a specific frequency without a digital display, so a digital frequency display should be a "must" for any shortwave radio you’re considering. However, an analog readout shortwave radio can make a good, inexpensive "spare" radio for traveling, etc.

• Modes. Some shortwave radios tune only AM mode stations, and these can be satisfactory for listening to most shortwave broadcasting stations. However, SSB is used by a few broadcasting stations in addition to ham, aeronautical, military, and maritime communications. A shortwave radio that can receive SSB in addition to AM will greatly expand your listening options on shortwave.

• Selectivity Options. Selectivity is discussed in more detail below, but you need to consider how many selectivity bandwidths you can select. Some portable receivers allow you to choose between "wide" and "narrow" selectivity bandwidths, while some desktop shortwave radios have as many as five selectivity bandwidths. Narrow selectivity bandwidths let you reduce interference from stations on adjacent frequencies, although the audio quality of the desired station will be reduced as the selectivity is narrowed.

• Antenna Connections. Some portable radios come with a built-in telescoping antenna but have no provision for an external antenna. Other portable shortwave radios have a jack that let you connect an external antenna. Most tabletop shortwave radios have connectors for external antennas. These usually include connectors for antennas using 50 ohm coaxial cables and others for antennas using ordinary insulated "hook-up" wire. External antennas normally give better reception than built-in antennas, although built-in antennas are usually satisfactory for listening to major international broadcasting stations. However, built-in antennas give poor results inside buildings with steel frames, like a high-rise condominium or apartment buildings. In such cases, the ability to connect an external antenna (even it is only a few feet of wire outside a window) can make a significant improvement in reception.

Here are some of the terms you need to understand when buying a shortwavr radio. These terms are used to describe the features and controls found on shortwave radios:

Audio filter. This circuit rejects certain audio frequencies in the audio output of a receiver. A bandpass filter will pass a certain band of audio frequencies but reject others. A low pass filter will reject all audio frequencies above a certain frequency. A high pass filter rejects all audio frequencies below a certain frequency.

Automatic gain control (AGC). This circuit adjusts the gain of the receiver to maintain a relatively constant level of audio output from the receiver regardless of changes in the strength of the received signal. Some AGC circuits let you select how fast it reacts to a change in signal strength, such as a "slow" or "fast" AVC. This circuit is sometimes called an automatic volume control (AVC).

Beat frequency oscillator (BFO). A circuit that produces an internally-generated carrier to allow reception of SSB, CW, and FSK signals.

Crystal lattice filter. This device improves selectivity by increasing rejection of signals on adjacent frequencies.

Digital signal processing (DSP). Circuitry in which analog signals, such as audio or radio signals, are converted into digital form, manipulated and processed while in digital form, and then converted back to analog form.

Dynamic range. A measure of the strongest received signal that a receiver can handle with overloading or distortion. It is measured in decibels. A minimum satisfactory measurement is 70 dB; over 100 dB is preferred.

Memories. These allow storing of frequencies of favorite stations. Some receivers allow storing of mode, receiver bandwidth, etc., in addition to frequency.

Noise blanker/limiter. This circuit reduces noise due to electrical equipment, lightning, neon lights, etc. Noise limiters are simpler circuits that limit the maximum strength of noise pulses, while more complex noise blankers actually silence the receiver during noise pulses. While this circuits can help reduce noise, they cannot eliminate noise and often introduce some audio distortion.

Notch filter. A notch filter removes a very narrow slice from a received signal, either from the radio frequency itself ("RF notch") or from the audio output ("audio notch") of the receiver.

Passband tuning. A circuit that allows you to move the selectivity bandwidth above or below the frequency to which the radio is tuned. This is often helpful in reducing interference.

Product detector. This is a beat frequency oscillator with enhancements for improved SSB and CW reception.

RF attenuator. This circuit reduces the sensitivity of the receiver in discrete steps, such as 10 or 20 decibels.

RF gain. A control that permits the sensitivity of a receiver to be continuously varied.

Scanning. This feature lets the receiver automatically tune through a desired frequency range, stopping on all frequencies where a signal is present. This feature is sometimes not too useful on shortwave, since atmospheric noise can also can mimic a radio signal.

Selectivity. The ability of a shortwave radio to reject signals on frequencies adjacent to the desired station. It is usually expressed as a bandwidth measured at 6 dB rejection points ("6 dB down" or "-6 dB"). For example, a selectivity specification of "6 kHz at -6 dB" means any signal outside the 6 kHz bandwidth will be reduced in strength by at least 6 dB (in other words, the interfering signal is only one-fourth as strong as it would be otherwise). Typical good selectivity measurements at 6 dB points are 6 kHz for AM, 2.5 kHz for SSB, and 0.5 kHz for CW.

Sensitivity. The ability of a shortwave radio to respond to weak signals. It is measured in microvolts (mV). The lower the measurement in microvolts, the fainter the signal the radio can receive.

Squelch. This quiets the receiver audio until the strength of a received signal exceeds a desired level.

Synchronous detection. A circuit that replaces the carrier in a received AM signal with an internally generated replacement to reduce the effects of fading. This useful feature is found in some portable radios like the Sony ICF-SW7600GR and also in some table-top models like the Drake R8B.

Variable bandwidth tuning. This circuit allows the selectivity of a receiver to be continuously varied.

Reporting and QSLs

"QSL" is the radiotelegraph code meaning "I confirm." In shortwave listening, a "QSL" is a card or letter from a radio station confirming that the recipient indeed heard the station.

In the early days of radio, stations were eager to know how well they were being heard. To encourage listeners to write in and report their reception, stations offered to send listeners souvenir cards and letters Soon SWLs began to collect these QSLs from stations as avidly as many people collect sports cards today.

Most international broadcast stations today use regular monitors to assess how well they are being heard and no longer rely upon listener letters. However, most broadcasters still respond to listener reception reports with QSL cards or letters. Many SWLs have amassed impressive, colorful collections of these souvenirs of their listening experiences.

A rare QSL! This is from KUSA, an experimental digital AM station that operated on 1660 kHz for a few days during the 1995 National Association of Broadcasters convention in Las Vegas. This was the first use of digital modulation on the AM broadcasting band---a bit of history preserved in this QSL card!

To receive a QSL from a station, you need to send a "reception report" to the station giving information about what you heard, the reception conditions, and what you liked (or didn’t like) about their programming. A good reception report should include the following:

  • the date and time (in UTC) you heard the station
  • the frequency on which you heard the station
  • details about what you heard sufficient to establish that you indeed heard the station; these are things like names of announcers and programs, titles of musical selections, station slogans, etc. (be sure to include the times you hear the various items)
  • an evaluation of the signal quality, including strength, degree of fading, and any interference you were experiencing (include the names and frequencies of interfering stations)
  • the make and model of radio you are using, along with any external antenna you use
  • comments and suggestions about the station’s programming

That last element is very important, since most international broadcasters today rely upon reception reports more for listener input about programming than they do for information on how well they are being heard. Don’t be afraid to candidly state what you really liked or disliked about their programming, and feel free to make suggestions about what you would really like to hear. Some major changes have been made as a result of these suggestions. For example, at the height of the Cold War in the late 1960s, the USSR’s Radio Moscow referred to American men who had no formal government title, such as "Governor Smith," simply by their last names, as in "Smith" and "Jones." A letter from an American listener pointed out that this sounded rude and uncultured, and that letter was read on Radio Moscow’s "Moscow Mailbag" program. The hosts said they were unaware of how this was perceived and no offense had been intended, and from that day forward Radio Moscow used the title "Mister" when referring to American men in its newscasts and commentaries!

Some stations like to receive signal information in the "SINPO" code. SINPO stands for signal strengthinterference, atmospheric noise,propagation, and overall reception quality. Each factor is rated on a 1 (worst) to 5 (best) scale, with a report like SINPO 55555 indicating the reception quality you get from a local AM or FM broadcaster. However, I prefer to describe reception quality in words, since I can give more useful information to the station that way.

To encourage frequent reception reports, many international broadcasters change designs of their QSL cards frequently and offer special series of cards that require you to send reports at regular intervals. In the late 1980s, for example, Radio Denmark offered a set of QSL cards that formed a painting when all cards were collected. Other stations send out stickers, decals, and pennants made of paper, plastic, or cloth to regular reporters. And a reception report to a station will typically get you on their mailing list for program schedules for years to come.

Not all shortwave broadcasters actively seek reception reports, especially stations in smaller nations that are privately owned and operated (as is often the case in Latin America). Here you must get creative in order to get the station to reply. While English can be used when reporting to major international broadcasters, you should always report in a major language used in that nation when reporting reception of smaller shortwave stations. (Reporting guides for such languages as Spanish, French, and Indonesian are available from shortwave equipment dealers.) You should also include some souvenirs of your area, such as picture postcards, commemorative stamps, etc. It also helps to prepay the postage for a reply. The easiest way to do this is with mint stamps of the country; these can be obtained from stamp dealers or from individuals who sell these to the SWLing and ham communities. Sending along $1.00 in U.S. currency to pay for postage is becoming increasing popular. Finally, you could send along two or three international reply coupons (IRCs), which are available at larger post offices.

To find the correct address to send your reception report to, consult a publication such as Passport to World Band Radio or the World Radio TV Handbook. These publications will also include information as to what languages you can send reports in, whether return postage should be sent, and which station personnel should receive your letter. Always send your reports via air mail; the extra cost over surface mail is a small price to pay for the extra speed and reliability of air mail service.

Some non-broadcast stations—especially time signal stations, maritime stations, and hams—will also reply to listener reports, especially if the listener prepares a QSL card and sends it along with their report. However, many non-broadcast stations will simply ignore reception reports since they couldn’t care less how well they are being received by the general public.

A lot of people enjoy shortwave listening without bothering to send reception reports and collecting QSLs, and indeed there are several listeners (and stations) that consider the entire practice to be a waste of time and energy. However, I enjoy these tangible memories from my listening "career." Today, I especially treasure my QSLs from stations in countries like the USSR, Czechoslovkia, East Germany, and other countries that no longer exist. These are pieces of history I’m glad I decided to obtain!

Introducing the "Action Bands"

Listening to the "action bands"—that is, those frequencies above 30 MHz—on a scanner radio may well be the most popular of all hobby radio activities. And it's a relatively new activity, as the first scanner radios weren't introduced until about 1970.

A scanner radio is one that automatically tunes through a set of frequencies, usually called "channels," at a predetermined rate. When the scanner finds a signal on a channel, it pauses there to let you hear the communications. When the signals end on a channel, the scanner resumes tuning through its channels until it finds another "active" channel.

Scanners were a real boon to listeners because most transmissions above 30 MHz are brief, and operating frequencies are quiet for long periods between transmissions. Older radios that tuned above 30 MHz had to be manually retuned to change frequencies. If you were tuned to the frequency used by your local police department, for example, you would miss a call on the frequency used by your local fire department.Scanners made it possible to keep track of several different channels simultaneously.

The first programmable scanners were introduced in the late 1970s, and this really boosted the popularity of scanner listening. The first scanners required to you to install new frequency-controlling crystals each time you want to receive a new frequency. Not only was this expensive, there was often a delay of weeks before new crystals "cut" to the desired frequencies arrived. Programmable scanners make changing frequencies as easy as tuning a new station on an AM or FM radio. Most scanners today also have a search function that lets you seek out active frequencies that you're not aware of.

Here is a sampling of what can be heard on a typical scanner:

  • Police, fire, and emergency services. Few things are as gripping as listening to the police in pursuit of criminals, firefighters attempting a rescue inside a burning building, or an ambulance rushing to the hospital!
  • Aviation. Civilian aircraft and airports can be heard from 108 to 136 MHz, while military aircraft are found from 225 to 400 MHz.
  • Marine communications. 156.80 MHz is the ship calling and emergency channel, with several other channels near it. This frequency is used on rivers, lakes, etc., in addition to the oceans.
  • Government. Federal, state, and local governments are heavy users of the bands above 30 MHz. Listening can range from law enforcement agencies to your local sanitation and road maintenance services. This is a great way to keep track of how your tax dollars are being spent!
  • Ham radio. Ham radio operators are found at 50 to 54 MHz, 144 to 148 MHz, and several other bands.
  • Private businesses. You can hear the activities of businesses ranging from taxicab companies to motion picture crews on your scanner.
  • Miscellaneous. Wireless microphones, weather bulletins, and even garage door openers can be received on most scanners.

Most communications heard above 30 MHz will be in FM, with the exception of AM on the aeronautical bands. Propagation on the bands above 30 MHz is usually restricted to "line of sight." This is defined as the optical horizon as viewed from the receiving antenna plus about another 15% due to radio signal "bending" caused by the Earth's curvature. While receiving range can be increased by using an outdoor antenna mounted high in the air, most signals heard above 30 MHz will be within 100 miles or less. However, under unusual propagation conditions, stations on the 30 to 50 MHz band can be heard from hundreds or even thousands of miles away.

To improve coverage, many users of the frequencies above 30 MHz employ repeater stations. A repeater station is located on top of a mountain or tall building, and automatically re-transmits a signal received on one frequency (the input frequency) on a second frequency (the output frequency). Some favorably located repeater stations can be reliably heard at distances of over 150 miles.

For listening to radio services within a radius of about 30 miles or so, an indoor scanner antenna, like the telescoping "whip" built into many scanners, is adequate. However, reception range and signal strength will be greatly improved if you use an external outdoor antenna.

While you're generally free to listen to anything tuned by a scanner (except cellular telephone calls, wireless intercoms and cordless phones), Section 705 of the federal Communications Act prohibits divulging or using the contents of any message you hear not intended for the general public. In practice, this is widely ignored; many wrecker and towing services have scanners in their offices to keep up with traffic accidents where their services might be needed, for example. Nonetheless, the law is on the books and could be enforced. It is prudent to not divulge the contents of anything you hear on a scanner.

In 1992, Congress went further and outlawed the sale and manufacture of scanners that can tune the cellular telephone bands. There have been attempts since then at the federal level to restrict scanning listening, but all have been unsuccessful.

Various states and localities have tried to restrict the use of portable or mobile scanners in an attempt to cut down on "ambulance chasing" and similar activities. States like New York and New Jersey have criminalized the use of a scanner to hamper police, fire, and emergency services or in the commission of a crime. A local scanner dealer can give you details about any restrictions in your area.

The World Above 30 MHz

Since VHF and UHF propagation is usually "line of sight," frequency allocations and usage are far more "localized" on frequencies above 30 MHz. However, there are some broad allocations for different purposes used in the United States and most of the rest of the Americas. The following is a summary of the main frequency bands found above 30 MHz. Please remember that listening to cellular phones, cordless phones and wireless intercoms is illegal in the United States.

30 to 50 MHz: This is known as the "VHF low" band. Most transmissions will be in narrow band FM with channels spaced at 20 kHz intervals. A wide variety of stations can be heard on this range, including businesses, federal, state, and local governments, law enforcement agencies, and various industrial radio services.

50 to 54 MHz: This is the six-meter ham radio band. The first megahertz is mainly used for USB, AM, CW, FSK modes, digital modes. The remainder of the band is used for narrow band FM, both simplex and through repeaters. 52.525 MHz is widely used as a simplex and calling frequency.

54 to 72 MHz: Television channels 2, 3, and 4 are located in this range. The video portions will sound like distorted noise on a scanner. The audio portions are in FM, but will sound "clipped" and "tinny" unless your scanner can tune this range in wide band.

72 to 76 MHz: This range is used for remote control signals for model airplanes and garage door openers, wireless microphones(including those used by law enforcement agencies), and two-way communications inside factories, warehouses, and other industrial facilities. Most channels are spaced at 20 kHz intervals.

76 to 88 MHz: This range is used for television channels 5 and 6.

88 to 108 MHz: This is where the FM broadcasting band is located.

108 to 136 MHz: This band is used for civilian aeronautical communications and all transmissions are in AM. Aeronautical beacons occupy 108 to 118 MHz; these continuously transmit a station identification and are used for navigation. The rest of the band is used for traffic between aircraft and air traffic control towers on channels spaced at 25 kHz intervals.

136 to 138 MHz: This segment is mainly used by weather satellites to transmit photographic images. 

138 to 144 MHz: The various military services are the biggest users of this segment in the United States, with most transmissions in narrow band FM and spaced at 5 kHz intervals. You can also hear ham radio operators who are members of the military affiliate radio service (MARS).

144 to 148 MHz: This is the two-meter ham radio band. This is the most heavily used ham radio band in the United States. USB and various FSK modes are mainly used in the first 500 kHz, and the rest of the band is FM. Most activity is through repeaters, although simplex activity is found on frequencies like 146.52 MHz. For more information about this band, visit the ham radio section of this site.

148 to 150.8 MHz: The usage here is similar to the 138 to 144 MHz range.

150.8 to 174 MHz: This is known as the "VHF high" band, and it is used by the same wide spectrum of users as the 30 to 50 MHz band.

174 to 216 MHz: This range is used for television channels 7 through 13.

216 to 220 MHz: In the United States, this band is used by the automated maritime telecommunication system (AMTS) used on major inland waterways such as the Great Lakes and the Mississippi river. Communications are in FM on channels spaced at 12.5 kHz intervals. However, the 219 to 220 MHz range is shared with ham radio. On this range, ham stations can be used to relay digital messages to other hams, subject to a maximum power of 50 watts. Hams must first register to use their shared allocation, and cannot use it within range of maritime users.

220 to 222 MHz: This range was reallocated a few years ago from ham radio to land mobile radio. Frequency usage and modulation have not yet been finalized, although new narrow bandwidth modes are expected to be used.

222 to 225 MHz: This is the 1.25-meter ham radio band. It is mainly used for FM communication through repeaters, although it is much less heavily used than the two-meter band.

225 to 400 MHz: This very wide band is used for military aviation communications in AM. Most channels are 100 kHz apart.

400 to 406 MHz: This range is used primarily by government and military stations in FM.

406 to 420 MHz: In the United States, this band is used exclusively by the federal government. All transmissions are in FM, with most channels spaced at 25 kHz intervals.

420 to 450 MHz: This is the 70-centimeter ham radio band, second in popularity to the two-meter band on VHF/UHF. The 420 to 444 MHz range is used for USB, digital modes, ham television, and ham communications satellites. The 444 to 450 MHz range is used for FM, mainly in conjunction with repeaters.

450 to 470 MHz: This is the "UHF" band on most scanners, used for many of the same purposes as the 30 to 50 and 150.8 to 174 MHz bands

470 to 512 MHz: This is known as the "UHF-T" band, and covers the same frequency range as television channels 14 to 20. This band is used for many of the same purposes as the "UHF" band in areas of the country without television stations on those channels.

512 to 825 MHz: This range is where television channels 21 through 72 are located.

825 to 849 MHz: This range is used for cellular telephone service, with cellular units transmitting here. Listening in this range is prohibited.

849 to 851 MHz: This band is used to provide telephone service from aircraft in flight. SSB is generally used here. Listening in this range is prohibited.

851 to 866 MHz: This is used by many of the same users as the 450 to 470 MHz band, with channels spaced at 25 kHz intervals.

866 to 869 MHz: This allocation is used by public safety and law enforcement agencies.

869 to 894 MHz: This range is used for cellular telephone service, with cells transmitting here. Listening in this range is prohibited.

894 MHz and above: These higher frequencies are where new communications technologies, such as wireless local area networks, spread spectrum telephony, and direct satellite broadcasting are being implemented.

Selecting a Scanner

Scanners are much different than other consumer-level radios----or even shortwave radios, for that matter. If you're looking to buy your first scanner radio, you probably feel a bit confused and overwhelmed by the features and specifications of the models you're considering!

As with most consumer items, there is no one "best" scanner radio for everyone. For example, if you want to simply listen to your local police and fire departments, a basic, low cost scanner will do fine. On the other hand, you can easily spent over $1000 for a scanner capable of high performance over a broad frequency range in a variety of modes.

General Considerations

The first thing you need to consider about any scanner is what frequency ranges you're interested in monitoring. To get a better idea of what can be heard on different ranges, click here to visit The World About 30 MHz section of this site.

Portable scanners have become popular recently. Some are small enough to fit into a shirt pocket and let you follow the action at sporting events, exhibitions, shows, accident scenes, etc. However, a portable scanner will usually cost more than a home (or "base") unit of comparable features and performance. And remember that having a scanner visible at certain places and events can result in a quick escort out the door! Many avid scanner fans have both a home scanner and a portable unit.

Scanners really differ in the number of channels you can program in them. Some low cost scanners only have a couple of dozen channels available, while some deluxe scanners have 1000 or more channels you can program. The best advice here is to buy a scanner with more channels than you think you will need, as you'll probably run across interesting new frequencies you want to monitor. Maybe the most common wish of scanner fans is that their radios had more channels!

Make sure you understand how new frequencies can be programmed into a scanner. Some scanners will let you enter new frequencies only in specific increments, such as at 5 kHz intervals. Others force you to use the standard spacing between channels commonly used on a given band. More advanced scanners let you enter frequencies down to a single kilohertz. A scanner that tunes only in fixed increments means you may miss hearing some interesting things.

Most scanners automatically tune narrow band (that is, deviation of 5 kHz or less) FM on all frequencies except for the 108 to 136 and 225 to 400 MHz aviation bands, where AM is used. Some scanners allow you to receive wide band FM (deviation of 10 kHz or more) as well. This will let you monitor the FM broadcast band, television audio, and some government transmissions. However, use of wide band FM outside of the FM broadcast band and television channels is rare. A few scanners, such as the Icom R10 let you receive SSB as well, but SSB is seldom used above 30 MHz outside the ham radio bands, and even there narrow band FM heavily dominates. For most listening, a scanner that tunes narrow band FM (and AM on the aviation bands) should be more than adequate.

If you would like to monitor scanner frequencies and AM and shortwave, then consider a wideband receiver. Such radios offer exceptional frequency coverage and models such as the Icom R5 are quite affordable.

Understanding Specifications

The importance of the specifications indicating a scanner's performances largely depends on where you live. If you live in a large urban area, you will need a high degree of selectivity (the ability to reject interfering signals) because of the large number of radio signals found in urban areas. If you live in a rural area with few stations, then greater sensitivity (the ability to detect weak radio signals) will be more important.

Sensitivity is measured in microvolts, abbreviated mV. The lower the number of microvolts, the weaker the signal that the scanner can detect and produce intelligible audio from.

Selectivity is measured in kHz for a certain level of interference rejection. This rejection is measured in decibels (dB), usually at 50 dB. A "50 dB" rejection means an interfering signal is reduced to a level 100,000 times weaker than its actual strength. If a scanner has a selectivity specification of "40 kHz at 50 dB," this means signals 40 kHz or more away from the signal you want to hear are reduced in strength 100,000 times.

If you live in a rural area, good sensitivity is more important than good selectivity. With fewer stations to hear, you need to be able to catch weak signals and don't have to worry as much about interference. In an urban area, the opposite is true; your main concern is in rejecting interference from stations on adjacent channels, not catching weak signals. In a rural area, narrow band FM selectivity of 40 kHz at 50 dB will usually be adequate, while in an urban environment you will usually need selectivity of 30 kHz at 50 dB or better.

Signals can also "mix" in a scanner's internal circuits, producing false signals known as images. Images are an unavoidable by-product of a scanner's circuitry, but the better scanners can reject most of these phantom signals and reduce their strength. Image rejection is how this is measured, and a good scanner should have image rejection of 50 dB or greater.

While there are some exceptions, as a general rule you do get what you pay for in scanner performance. More expensive models will have better sensitivity, selectivity, and image rejection than less expensive units.

Some municipalities use trunking systems whereby a group or block of frequencies are used on a rotating basis. To properly copy such transmissions, you will need a Trunk Tracking scanner such as the Bearcat BC245XLT with Trunk Tracking that can "follow" the various channels as they are used and changed.

Some municipalities are now transmitting in APCO25 digital voice mode. Traditional scanners cannot "decode" these voice transmissions. Some of the newer scanners such as the Bearcat BC296D can handle both Trunk Tracking and Digital transmissions.

Scanner Features and Controls

Here are explanations for features and controls commonly found on scanners:

  • Attenuator. This reduces the sensitivity of a scanner in order to reduce images and other effects of strong nearby signals.
  • Audio squelch. This resumes scanning if a signal has no audio on a channel after pausing on the channel for a few seconds.
  • Autoload. This automatically stores new frequencies found during a search into the scanner's memories.
  • Bank. This is a way of dividing a scanner's channels into smaller, manageable blocks for specific purposes.
  • Delay. This determines how long a scanner pauses on a channel for another transmission before resuming scanning.
  • Hold. This lets you stop scanning on a channel so you can monitor it continuously.
  • Lockout. This causes the scanner to skip over a channel during its scanning sequence.
  • Priority channel. When a signal is present on a priority channel, the scanner switches to it regardless of whether signals are present on other channels being scanned.
  • Search. With this, the scanner tunes through a range and stops when an active frequency is found. This is very handy for finding new stations and users not listed in frequency directories.
  • Squelch. This silences the scanner's audio until a signal of a certain strength is received. The squelch level can be manually set.

National Scanner Frequency Guide

Most frequencies above 30 MHz are assigned on a local basis. To know where to listen for your local police or fire department, you'll need a frequency guide or directory for your locality. However, some frequencies, particularly those used for emergency or inter-agency communications, have been allocated nationally. The following is a list of some of the more widely used and active national frequencies. Program these into your scanner and get see what you can hear!

34.90: This channel is used nationwide by the National Guard during emergencies.

39.46: Used for inter-department emergency communications by local and state police forces.

47.42: This is a channel used across the United States by the Red Cross for relief operations.

52.525: This is a calling frequency used by ham radio operators in FM on their six-meter band. During periods of exceptional propagation, this frequency is filled with signals from hundreds or even thousands of miles away. If you're hearing distant signals here, then the 30 to 50 MHz range is also open for long distance reception.

121.50: This is the international aeronautical emergency frequency.

138.225: This is the prime disaster relief operations channel used by the Federal Emergency Management Agency; it is active during earthquakes, hurricanes, floods, and other catastrophic events.

146.52: This frequency is used by ham radio operators for non-repeater communications on the two-meter band; it is very busy in many parts of the country.

151.625: This channel is used by "itinerant" businesses, or those that travel about the country. Circuses, exhibitions, trade shows, and sports teams are some of the users you can hear. Other widely used itinerant channels are 154.57 and 154.60.

154.28: Used for inter-department emergency communications by local fire departments; 154.265 and 154.295 also used.

155.160: Used for inter-department emergency communications by local and state agencies during search and rescue operations.

155.475: Used for inter-department emergency communications by local and state police forces.

156.75: This channel is used internationally for broadcasts of maritime weather alerts.

156.80: This is the international maritime distress, calling, and safety channel. All ships must monitor this frequency while at sea. It is also heavily used on rivers, lakes, etc.

162.40: This channel is used for NOAA weather broadcasts and bulletins.

162.425: This channel is used for NOAA weather broadcasts and bulletins.

162.45: This channel is used for NOAA weather broadcasts and bulletins.

162.475: This channel is used for NOAA weather broadcasts and bulletins.

162.50: This channel is used for NOAA weather broadcasts and bulletins.

162.525: This channel is used for NOAA weather broadcasts and bulletins.

162.55: This channel is used for NOAA weather broadcasts and bulletins.

163.275: This channel is used for NOAA weather broadcasts and bulletins.

163.4875: This channel is used nationwide by the National Guard during emergencies.

163.5125: This is the national disaster preparedness frequency used jointly by the armed forces.

164.50: This is the national communications channel for the Department of Housing and Urban Development.

168.55: This is the national channel used by civilian agencies of the federal government for communications during emergencies and disasters.

243.00: This channel is used during military aviation emergencies.

259.70: This channel is used by the Space Shuttle during re-entry and landing.

296.80: This channel is used by the Space Shuttle during re-entry and landing.

311.00: This is an active in-flight channel used by the U.S. Air Force.

317.70: This is an active channel used by U.S. Coast Guard aviation.

317.80: This is an active channel used by U.S. Coast Guard aviation.

319.40: This is an active in-flight channel used by the U.S. Air Force.

340.20: This is an active channel used by U.S. Navy aviators.

409.20: This is the national communications channel for the Interstate Commerce Commission.

409.625: This is the national communications channel for the Department of State.

462.675: This channel is used for emergency communications and traveler assistance in the General Mobile Radio Service.

Ham Radio

According to the Federal Communications Commission, amateur ("ham") radio is:
A radio communications service for the purpose of self-training, intercommunication, and technical investigations carried out by amateurs, that is, duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.

But that definition leaves out something very important: ham radio is a lot of fun!

If you're interested in hobby radio at all, ham radio is the ultimate trip: the chance to operate your own radio station. Want to communicate around the world on shortwave? Want to use VHF and UHF frequencies like you can hear on a scanner? Want to operate your own television station? The ultimate model radio control system? Want to experiment with packet radio----an on-the-air version of the Internet---or "go retro" with Morse code? Ever wondered what it would be like to communicate directly with a ham aboard the Space Shuttle or through a communications satellite using your own radio station? You can do all of that, and a lot more, with ham radio.

Many ham radio operators like to exchange QSL cards with each other after a QSO (contact), especially with a distant station or one in a different country.

One thing needs to be made clear up front: all ham radio communications are restricted to two-way communications with other ham radio stations.You can't broadcast on the AM or FM broadcast bands with a ham radio license, nor can you communicate with other two-way radio stations, like CB or marine stations, via ham radio except in emergencies.

Ham radio operators have several different frequency bands set aside for their use. These bands range from just above the AM broadcast band (the AM band ends at 1700 kHz; the 160-meter ham band begins at 1800 kHz) through the shortwave band and into the VHF, UHF, and microwave frequencies. The exact frequency ranges that you can use depends upon the class of ham radio license you hold.

. . . . . Ah yes, licensing! To operate a ham radio station in the United States, you must hold a license issued by the FCC. Obtaining a license requires you to pass an examination; higher license classes require passing more difficult exams.

Actually, requiring exams before issuing a ham license makes a lot of sense. Most of the topics on the written exams are things you need to know anyone in order to properly and safely operate your station. All ham license classes but one (the Novice class) allow you to use transmitter powers as high as 1500 watts (compare that to the 5 watts CB stations are allowed!). You can use a variety of different modulation modes on frequencies capable of worldwide communication-----and interference! Those are some very good reasons for determining someone's competence via examination before granting a ham radio license. Don't look at the exam requirement as an obstacle; instead, think of it as an opportunity to demonstrate how good you are.

But don't you have to pass a Morse code test to get a ham radio license? The good news is: THE MOST POPULAR CLASS OF HAM RADIO LICENSE REQUIRES NO MORSE CODE TEST! That class of license is the Technician. To get it, you have to pass an exam consisting of 35 multiple-choice questions. If you answer 74% or more correctly, you're a ham! As of February 2007 the Morse Code requirement was dropped for ALL amateur license levels. There is absolutely no more code requirement for amateur radio.

And the news gets better: all questions on the written ham radio exams are drawn from a public "pool" of questions. In the case of the Technician exam, the 35 questions are drawn from a pool of  510 questions, all of them multiple-choice. Several ham radio exam study guides based upon the question pools are available. Even though it's best to learn some basic electronics before taking the Technician exam, it's possible to get a ham radio license just by memorizing the pool questions and answers!

The Technician class of license restricts you to operation on frequencies of 50 MHz and above. As you may know, these frequencies are in the VHF/UHF range typically covered by scanner radios. Aren't these frequencies good only for local, "line of sight" communications?

No! The 50 to 54 MHz range (known as the six-meter band) "opens" several times each year for communications over ranges of hundreds or even thousands of miles away through a phenomenon known as sporadic-E propagation. During years of high sunspot activity, the six-meter band can be used for regular communications worldwide, similar to the 10-meter (28 to 29.7 MHz) band. Several hams have managed to contact over 100 different countries on six meters.

Some ham radio operators like to go on "DXpeditions," which are trips to countries where few ham radio operators are active. The "DXpeditioners" put the rare country on the air and try to make as many contacts as possible. This is a QSL card from a DXpedition to the Cayman Islands.

The Technician license also lets you operate on the two-meter (144 to 148 MHz) band. "Two" is the world's most popular ham radio band. Reliable range on this band is normally restricted to the visual horizon plus about 15% extra. Depending on your local terrain, this works out to about 20 to 50 miles from your location. However, hams have developed some ingenious ways to extend this range.

One is the repeater station. A repeater station listens for a signal on one frequency (the input frequency) and re-transmits, or "repeats," it on another frequency known as the output. Repeater stations are located on top of tall buildings or mountains where the "radio horizon" is much greater than from the ground. It's not uncommon for a hand-held "walkie-talkie" two-meter transceiver (combination transmitter/receiver) to be able to reliably communicate over a radius of a couple of hundred miles through a repeater.

Technician class hams are also able to communicate through ham radio communications satellites. Most ham radio satellites make some use of the two-meter band, either for ground-to-satellite (uplink) or satellite-to-ground (downlink) signals. Many hams have contacted over 100 different countries via communications satellites. Equipment and antennas for satellite communications can be very modest; satellite antennas for two-meters are similar in size to outdoor TV/FM antennas.

Other activities open to Technician class hams include packet radio, amateur television, model control, and friendly chatting ("ragchewing") with other hams in their area. Most communications on the ham bands above 50 MHz use FM, but SSB, digital modes, and even Morse code (CW) are used.

International regulations formerly required a Morse code exam for operation on frequencies below 30 MHz, but this has been by dropped by the United States and many other countries.

This isn't a sexist QSL card; OH2MEL is a YL (unmarried female) ham radio operator in Finland.

Each license class conveys a different set of operating privileges, with the Technician class license giving the most narrow set of privileges on a limited number of bands and the Extra giving all amateur privileges on all bands. Hams also get distinctive call signs reflecting their class of license. For example, a call sign like KZ9ZZZ would be normally be issued to a Technician licensee while AK6C would be issued to an Extra class licensee. In the United States, the numeral in a ham's call sign indicates where the ham was living when the license was originally issued.

Ham radio is an international fraternity that transcends the barriers of nationality, race, age, sex, and class. Whenever you take to the air as a ham, you never know who you might find to talk to. It might be an old friend you've known for years; it might be a new friend you haven't met before. Why not join the millions around the world who already have their ham license? They would all like to say hello to you!

AM Band

Each year, dedicated listeners manage to snag stations from thousands of miles away on the AM broadcast band (540 to 1700 kHz). In fact,the AM band is where DXing began.

Back in the 1920s, the first radio stations were anxious to know how far away they were being heard. They asked for reception reports from listeners, and promised to reply to reports with souvenir postcards confirming that the listener indeed heard the station. The entire hobby of "SWLing" grew from those beginnings!

Getting start in AM band DXing is easy—just tune across the AM band from your local sunset to your local sunrise! If you mainly keep your AM radios set to local stations, you may be surprised at how well you can hear stations from hundreds and even thousands of miles away at night using an ordinary AM radio.

In North and South America, AM stations are spaced on channels at 10 kHz intervals (540, 550, 560, etc.). Most AM stations are located from 540 to 1600, with new stations soon to take to the air in the 1610 to 1700 kHz. When you tune the AM band at night, you will soon discover that there are a lot of stations active on the AM band! Despite the seeming cacophony, AM band frequencies are carefully allocated into three categories: localregional, and clear channel.

Local channels are 1230, 1240, 1340, 1400, 1450, and 1490. Stations are limited here to a maximum transmitter power of 1000 watts and must use a non-directional antenna. These are very congested frequencies, with maximum reliable reception range at night usually restricted to less than 30 miles. (If you have no nearby stations on these frequencies, you will usually hear only a "rumble" at night on them.) However, reception at greater distances is possible with patience and good equipment. Local channels are often referred to as "graveyard" frequencies.

Stations on regional channels can use higher transmitter powers, typically up to about 20,000 watts, and directional antennas. As you might expect from the term "regional," these stations are intended to serve specific geographic areas. Regional stations often use different power levels and directional antennas for day and night operation; since AM band signals travel further at night, regional stations will reduce transmitter power and use a "tighter" directional antenna between their local sunset and local sunrise.

KLZ, 560 kHz, in Denver is a regional station. The "5 KW DA-U" notation on this QSL card means it operates with 5000 watts with a directional antenna for an "unlimited" (i.e., 24-hours per day) amount of time. This card was received for a special "DX test" (explained below).

The term "clear channel" is a misnomer today. Clear channel stations can use 50,000 watts of power and many use non-directional antennas. In the early days of radio, no other stations could operate on a clear channel station's frequency between sunset and sunrise. Because the channel wasliterallyclear and high transmitter powers were used, clear channel stations could be heard over much of the country at night.

Beginning in the early 1980s, additional stations were authorized to operate on clear channel frequencies at night, often with greatly reduced power and directional antennas. Many of the stations so authorized had previously been allowed only to operate during their local daytime, and lost listeners when they had to sign off at sunset. While the "breaking up" of clear channels may have been economically necessary for daytime-only stations, it did result in many clear channel frequencies sounding much like regional channels at night.

One practice that has continued since the early days of radio is the "DX test." FCC rules allow stations which must reduce power or change antennas at night to briefly test using daytime power and antennas during an "experimental period" from midnight to sunrise. A DX test is a special program transmitted after local midnight using higher transmitter power or different antennas than the station normally uses. Often, station identifications in Morse code are used; the Morse code will often make it through interference better than voice announcements. Most DX tests are arranged in conjunction with one or both clubs for AM band DXers to assure a large listening audience.

Outside of North and South America, AM stations operate on channels spaced 9 kHz apart (765, 774, 783, etc.). These so-called "split" frequencies means it is possible to hear AM stations from Europe, Asia, and Africa between the 10 kHz channels used in North and South America. Listeners along the east coast can hear European and African stations from their local sunset to about 0600 UTC, while Pacific Coast listeners can catch Asian stations from about an hour before sunrise to actual sunrise.

To hear such foreign stations, you will need a receiver with excellent selectivity and a high performance antenna. Many AM DXers use an indoor rotatable loop antenna with a preamplifier. A loop antenna will reject signals coming from right angles to it, and this helps reduce interference. Other AM DXers use "Beverage" antennas, which are wires in straight lines running for hundreds or thousands of feet.

The best time for long distance AM band reception is during the fall and winter months, with the period around the equinoxes being especially good. Stations located to the east of you will start fading in about an hour before your sunset, while stations to your west may remain audible up to an hour after your local sunrise.

There are currently two clubs specializing in AM band DXing, the National Radio Club and the International Radio Club of America. Both publish weekly bulletins during the fall and winter "DX season" giving news about what's being heard and upcoming DX tests. Both clubs also offer station directories and other publications of interest to AM band DXing specialists.

Take a spin across the AM dial tonight. You might be pleasantly surprised at what you can hear!


"Longwave" refers to all frequencies below the lower end of the AM broadcasting band at 540 kHz. The lower limit of what frequencies constitute "radio" is not precisely defined, but 5 kHz is a widely accepted starting point for the radio spectrum.

For many years, radio hobbyists ignored longwave because most commonly available communications receivers only tuned down to 540 kHz. However, most new receivers today tune down to at least 150 kHz and longwave DXing is enjoy new popularity.

One big problem when tuning longwave is electrical noise from power lines, electrical devices, motors, etc. Longwave is far more susceptible to such noise than higher frequencies, and you might hear only a loud "buzz" when you tune across longwave from your location. Also, static crashes from thunderstorms can be severe, especially in summer. To combat noise, many longwave DXers use an indoor "loop" antenna that allows rejection of nearby electrical noise sources. Other longwave DXers use special phasing units to reduce noise levels.

Reception distance on longwave is similar to that on the AM broadcast band, as are reception patterns. Greater range is possible when the signal is reaching you over a water path, as is often the case in coastal regions. At night, reception of stations from hundreds or even thousands of miles away is possible. Night reception on longwave is better in winter than in summer, and the equinoxes often give the best propagation.

Unlike the shortwave frequencies above 1700 kHz, the longwave spectrum is allocated on a more "ad hoc" basis, with different users and services frequently sharing the same frequency range. Here is a general description of the world below 540 kHz:

Below 155 kHz: Signals below 155 kHz don't propagate very well via the ionosphere; the absorption is too great even at night during winter. These signals can travel for thousands of miles via ground wave, but high transmitter powers are required. Signals at very low frequencies, about 50 kHz and lower, can penetrate sea water very well. As a result, these frequencies are used by military forces of the major powers, especially for communication with submarines. The U.S. Navy's "Omega" navigation system is found on 10.2, 12, and 13.6 kHz. The Russian navy operates a similar system on 15.62 kHz. The U.S. Air Force has a FSK-based communications system on 29.5 and 37.2 kHz. This system was established to provide a backup in case nuclear explosions rendered the ionosphere useless for propagation. Miscellaneous FSK-based stations are found here for direct communications with submarines and naval forces.

150 to 175 kHz: In the United States, this range is used by the U.S. Air Force's ground wave emergency network (GWEN), a packet-based network to provide communications during a nuclear war. Transmitters are kept continuously operational here on a "standby" basis, and it's easy to hear their loud, "raspy" signal bursts.

155 to 281 kHz: This is another AM broadcasting band in Europe and parts of Asia. In Europe, there are numerous high powered (1,000,000 watts or more) stations here. These stations are capable of covering an entire European nation like France or Germany with reliable signals around the clock. Although ionospheric propagation is not good at these frequencies, the high powers used means that many of these broadcasters can be heard along the Atlantic seaboard during the fall and winter. Best reception is usually from local sunset to about 0600 UTC. A few longwave stations in Asiatic Russia can be heard on the Pacific Coast beginning an hour or so before local sunrise.

160 to 190 kHz: In the United States, this range is open to unlicensed experimental transmissions. Transmitter power is restricted to one watt, and the maximum antenna length (including feedline) can be no more than 50 feet. Any mode can be used. Some of these "lowfer" (as they are known) unlicensed stations have been heard several hundreds of miles away under favorable conditions.

200 to 430 kHz: This range is used mainly by navigation beacons, which continuously repeat their call signs in Morse code. Call signs do not follow the international allocations given elsewhere on this site. Instead, the call signs usually give an idea of the location of the beacon. For example, beacon "FT" on 365 kHz is located at Fort Worth, Texas.

430 to 500 kHz: This range is used for two-way Morse code communications between ships at sea and shore stations. Shore stations use three-letter callsigns, while ship station callsigns consist of four letters. All callsigns are from international allocations. The number of stations you can hear in this range is rapidly declining due to a shift in maritime communications to satellites and shortwave frequencies. After February, 1999, radio operators skilled in Morse code were no longer required on ships sailing in international waters.

500 kHz: This was an international ship calling and distress frequency for maritime communications in Morse code. It is no longer used, and after February, 1999, ship stations and shore stations were no longer required to monitor this frequency for calls.

500 to 540 kHz: This segment is populated by miscellaneous beacons and stations. Perhaps the most interesting frequency here is 518 kHz, used for transmission of maritime safety and navigation information via FSK. This system is known as NAVTEX, and includes weather bulletins as well as notices of missing and overdue vessels. 530 kHz is used in the United States and Canada for low powered road and traffic information broadcasts.

Clandestine Radio

A clandestine radio station usually sounds like any other broadcasting station. However "legitimate" a clandestine station might sound, however, it is "extralegal" and deceptive in its operation. Here are some key elements that distinguish a clandestine broadcaster from "ordinary" broadcasters:
  • Clandestine broadcasters are deceptive. They often lie about their location, sponsoring government or organization, and their intentions. Programming is essentially propaganda, and may largely be half-truths or outright lies.
  • Clandestine broadcasters aim to bring about political changes or actions in a target country. They may want to incite revolution in another country or simply to influence the populace of the target country to be more sympathetic toward the country or organization operating the clandestine.
  • Clandestine broadcasters are temporary. Since the purpose of a clandestine is political, clandestine stations usually leave the air quickly when political situations change. Numerous clandestines were active in and around Vietnam during the late 1960s, but all went off the air when North Vietnam conquered South Vietnam in 1975.

Clandestine broadcasting began in World War II, with the Allied and Axis nations directing broadcasts toward each other. In fact, the longest-running clandestine station in history started in 1941. After Franco’s victory in the Spanish Civil War, the Spanish Communist Party set up a station called Radio España Independiente. This station at first broadcast from the USSR, and after World War II used transmitters in Eastern Bloc nations as well. It remained on the air until 1977, when it left the air following Franco’s death.

The busiest era for clandestine broadcasting was the 1960s. In addition to the stations active during the Vietnam War, China and the USSR operated clandestine broadcasters against each other as their ideological conflict worsened. For most SWLs in North America, however, the real excitement involved clandestine broadcasters directed against Cuba. The most famous of these was Radio Swan/Radio Americas.

Radio Swan first appeared on 1160 and 6000 kHz in May, 1960. The station claimed to be a commercial station broadcasting from Swan Island, an island in the Gulf of Mexico that was claimed both by the United States and Honduras. It broadcast entirely in Spanish, and its programs had a strong anti-Castro slant. Despite being on what the United States claimed as its territory, the FCC claimed it had no knowledge of Radio Swan.

QSL card from Radio Americas
Radio Americas solicited reception reports to a post office box in Miami, and replied with this colorful QSL card. The location of Swan Island is indicated by the station's name in the middle of the card. This card was received by Harry Helms for reception on 1160 kHz on May 18, 1966. In 1966, the only station on 1160 at night was KSL in Salt Lake City, and Radio Americas could be well heard east of the Rockies.

During the ill-fated May, 1961 Bay of Pigs invasion, Radio Swan transmitted coded messages to the invading forces. This resulted in widespread speculation that the station was actually a CIA operation. Later in 1961, Radio Swan changed its name to Radio Americas and remained on the air until it abruptly left the air in May, 1968.

As of 1997, the hot spot for clandestine radio activity is the Middle East, with Iraq being both the main target of, and the main instigator of, clandestine activity. Main stations operated against Iraq tried to stir up rebellion among Iraq’s Kurdish population. Iraq does the same with clandestines targeting Iran and Saudi Arabia. In Asia, both North Korea and South Korea operate clandestine stations directed against each other.

Colombia is home to two currently active clandestines, Radio Patria Libre and La Voz de la Resistencia. These are interesting because both apparently operate within Colombia itself from rebel-controlled areas. The frequencies of these two stations vary, but they are currently active from 6250 to 6260 kHz around 2200 to 2300 UTC.

Most clandestine stations are operated by governments, but a few are operated by private organizations with the tolerance of a host country. An example is the last remaining anti-Castro clandestine, La Voz del Cuba Independiente y Democrática (CID). Currently, this station is still heard sporadically during the evening and night hours in North America around 6305 kHz. It is rumored to be operating from Guatemala.

Pirate Radio

A "pirate" radio station is an unlicensed, illegal station broadcasting in violation of the laws of the country it is located in. Unlike clandestine stations, pirate radio stations are seldom political in nature (other than advocating "free radio" or legalization of marijuana). Instead, pirates are usually hobby broadcasters operated just for fun by their owners.

Pirate broadcasting is a relatively new development in North America. Prior to the late 1970s, there had been just a handful of unlicensed broadcasters in the United States and Canada. Most of these operated on the AM and FM bands, and were seldom heard outside their local areas. In the late 1970s, inexpensive used ham radio transmitting gear suitable for pirate broadcasting became widely available. Another factor was a growing inability of the Federal Communications Commission, along with Canada’s Department of Communications, to enforce regulations against unlicensed broadcasting. Soon after cracks started appearing in the "dam" of regulations, it broke; it is not uncommon now to have over a dozen pirate broadcasters active on shortwave from the United States and Canada in a single weekend.

Today, most pirate radio activity takes place in USB on frequencies above or below various ham radio bands. The most popular range for pirate operators is near the 40-meter (7000 to 7300 kHz) ham radio band. Pirates tend to congregate around a frequency that has little interference. For years, 7415 kHz was the de facto "standard" pirate radio frequency, while today most activity centers around 6955 kHz. Pirates coordinate their schedules to avoid causing interference to each other.

Most pirate activity in the United States and Canada takes place on weekend evenings and nights, with holidays like Labor Day, New Year’s Eve/Day, and President’s Day also popular. Historically, however, Halloween produces more pirate radio activity than any other night of the year!

If one station can be considered as the "starting point" for pirate radio today, that would be the Voice of the Voyager. This station took to the air in early 1978 on 5850 kHz from a location near Minneapolis, Minnesota. This station could be easily heard throughout North America, and it operated on a regularly schedule of late Saturday night. The operators were all SWLs themselves, and soon attracted a wide audience with their parodies of the FCC and SWLing clubs/personalities. They also played rock music, and broadcasts sounded very much like a group of young people having a party.

The Voice of the Voyager began a practice that is now standard for almost all pirate stations today—the "mail drop." A mail drop is a third party that agrees to forward mail to a pirate stations. A letter or reception report for a pirate station is sent to a mail drop along with two or three postage stamps, and the mail drop "operator" forwards the mail to the pirate. The Voice of the Voyager used a mail drop in Michigan.

Unfortunately for the Voice of the Voyager operators, the FCC’s St. Paul, Minnesota office raided and closed the station in August, 1978. The FCC officials seemed more amused than angry (they even asked for souvenir QSL cards), and issued no fines nor took any other actions against the operators. However, they were warned not to resume operations.

Enforced silence was too much for the Voice of the Voyager crew, however. They began to discreetly circulate word within the SWL community, especially among their previous listeners, that they planned to return to the air on November 5, 1978 on a new frequency of 6220 kHz. The original intent was to due a "farewell broadcast" and then cease operations forever, but the success of the November 5 broadcast inspired the operators to continue. Their actual final broadcast was not until January 14, 1979. This time, it wasn’t the FCC that took the station off the air; it was the failure of their aging transmitting equipment instead. (A few members of the Voice of the Voyager staff reactivated the station in 1982, but it was quickly located and shut down by the FCC.)

Pirate radio is among the most original you will ever hear. However, the program quality is highly uneven. At its worst, pirate radio is crude, imitative, and "high school" sounding. At its best, pirate radio can let you hear stunning original material, especially social and political satire, that you cannot find anywhere else on the radio dial.

For example, one station that has been active recently is Lounge Lizard Radio, which features music by Al Martino, Sammy Davis, Jr., Mel Torme, and other well known "cocktail music" artists. The station tries to simulate the atmosphere of a cocktail lounge. Another pirate station is KOLD, which programs mostly Big Band and boogie woogie music. A station that has been active for several years is Radio Free Euphoria, operated by "Captain Ganja." Captain Ganja—who genuinely sounds stoned on the air!—advocates the legalization of marijuana.

Because they are usually low powered and use simple antennas, pirate radio stations are more difficult to hear than most other shortwave broadcasters. This is especially true if you are located in western North America, since most pirates are found east of the Rockies. While you can hear some pirates on simple, inexpensive shortwave radios, you will hear far more on better quality desktop shortwave radios and an outside antenna.

Since most pirates do not operate on regular schedules, the best way to hear them is to keep an ear on frequencies where other pirates have recently been active. Currently, the most active pirate frequency is around 6955 kHz in USB, and most stations are active on weekend evenings/nights as well as major holidays. There is even a newsletter for those who enjoy listening to pirate stations published by theAssociation of Clandestine Radio Enthusiasts.


When the FCC allocated new frequencies for FM radio and television broadcasting after World War II, the frequencies chosen were believed to support only "line of sight" propagation. This would insure reliable local service and prevent stations from suffering interference from distant stations on the same frequencies.

Happily for DXers, the FCC was wrong. While frequencies above 54 MHz (the start of TV channel 2) normally support only line of sight propagation, there are several occasions each year when TV and FM signals from hundreds or thousands of miles away can be received on ordinary television sets and FM radios. No special equipment is needed, either. A cheap indoor "rabbit ears" antenna is adequate for pulling in spectacular TV and FM DX, for example.

It is not surprising that the FCC thought that TV and FM frequencies would be immune from long distance propagation, because the conditions that produce it are irregular, comparatively rare events. Long distance propagation on frequencies below 30 MHz is a regular, highly predictable phenomenon. On the TV and FM frequencies, however, it is unusual and largely unpredictable (although certain times of day and the year are more likely to experience it than others). Catching TV and FM DX is largely a matter of being on the right frequency at the right time!

The main sources of DX reception on TV and FM are sporadic-E and tropospheric ducting (or "tropo" as it is commonly known). Another source is "scattering" of signals off the ionized trails left by meteors. And, during years of exceptionally high sunspot activity, frequencies as high as TV channel 2 can be propagated via the ionosphere like a shortwave signal.

Sporadic-E propagation is caused by patches of intense ionization in the E-layer of the ionosphere (approximately 35 to 60 miles above the Earth's surface). Signals on frequencies above 30 MHz normally pass through the ionosphere and into space. However, sporadic-E "clouds" are capable of refracting such signals back to Earth. The term "clouds" is an apt way to describe the patches of highly charged particles that form during a sporadic-E event. Like clouds, these patches move and are highly irregular in size and shape. It is possible to track the movement of a sporadic-E "cloud" by noting the locations of stations that fade in and out on a frequency as the cloud moves.

Sporadic-E propagation can occur any time of day or year. However, sporadic-E is most common from about mid-May to late July, with another peak a week before and after the winter solstice. Sporadic-E seems to be most common from about mid-morning to noon, local time, and again from late afternoon through the evening hours.

The highest frequency that can be received via sporadic-E depends on how intensely ionized the cloud is. Sporadic-E is first noticed on TV channel 2 and then "rises" in frequency as the ionization intensity increases. Next affected are TV channels 3 and 4, followed by TV channels 5 and 6, and then the FM broadcast band. Only in very rare cases will sporadic-E propagation reach TV channel 7 or higher. A sporadic-E opening might "stall" at a certain frequency and go no higher. This means, for example, that you could be seeing distant TV stations on channels 2 and 3 yet conditions might be normal on other channels and the FM band.

The first sign that a sporadic-E event is starting is usually "rolling" black bars across TV channel 2 (or the appearance of signals on that channel if you have no local stations on it). As the ionization level increases, channels 3, 4, 5, 6, and the FM band becoming filled with signals. During sporadic-E propagation, signals can abruptly appear or disappear. Signals are usually very strong during sporadic-E. Ordinary "rabbit ears" are adequate for sporadic-E reception, and are preferred by some TV and FM DXers because they can be sharply directional.

Tropo propagation is caused by temperature inversions in the troposphere, the region of the atmosphere closest to Earth where all weather takes place. A temperature inversion is a point where air temperature actually increases with elevation. These often form along stationary or occluded weather fronts. A radio signal above 54 MHz in a temperature inversion is like water in a pipe; it is "trapped" and gets bent over the horizon for hundreds of miles.

The effects of tropo propagation increase with frequency. Tropo is far more common on the FM band and TV channels 7 and higher than it is on channels 6 and lower. Unlike sporadic-E, tropo signals tend to be steady, although usually of weak to moderate strength. Tropo propagation along a stationary weather front can last for hours or even days. Since signals are not as strong as sporadic-E, you will need an outside antenna to take full advantage of tropo.

Tropo is rare west of the Rockies, although it does happen along the California coast. It is far more common east of the Rockies, where warm, humid air masses from the Gulf of Mexico frequently meet drier, cooler one arriving from the Northwest. Tropo can happen along the line where those air masses collide. Hazy, foggy, and smoggy weather is a good sign that tropo propagation is possible. Tropo is most common during spring and fall, and during extended periods of humid, windless weather in summer.

A rare but exciting form of propagation is meteor scatter. The ionized trail left by a meteor burning up in the Earth's atmosphere is capable of refracting radio signals much like sporadic-E. Depending on the size of the meteor and the length of the trail it leaves, meteor scatter propagation can last from a second or two (called "pings") to over two minutes. Most reception times will be less than 30 seconds, but you may get lucky enough to hear (or see) identifying material during that interval. Like sporadic-E, meteor scatter mainly affects channels 2 to 6 and the FM broadcast band.

You can run across meteor scatter anytime, but the best time to try for it is during one of the yearly meteor showers that brings out stargazers.One of the most productive showers for meteor scatter DX is the Perseids, which peaks around August 12 of most years. There are other showers throughout the year, and you can find information about them, including projected times of their peak intensity, in astronomy magazines.

During years of exceptionally high sunspot activity, as was the case in 1990 and 1991, the F-layer of the ionosphere is capable of refracting signals above 54 MHz. Channel 2 is the most affected, with some rare propagation of signals on channels 3 and 4 as well. During these times, truly phenomenal DX is possible. For example, a TV station on channel 2 in Hawaii has been received in Florida via F-layer propagation! As sunspot numbers increase, F-layer propagation above 54 MHz should again be possible beginning in the fall of 1999.

If you are interested in chasing TV/FM DX, you may be interested in joining the Worldwide TV/FM DX Association. Their monthly bulletin contains information about recent TV/FM DX receptions plus articles on techniques for enhancing reception. Click here to visit their Web page.

If you have cable, invest in a simple "rabbit ears" antenna for your television, and maybe do the same for your FM stereo receiver. You might be really surprised at what you can see and hear with a little luck! And it you get smittin by the FM DXing bug, there are modestly priced, high performance antennas such as the Nil-Jon HD FM H4 beam available.




Ham radio is a hobby that appeals to young and old alike from all around the world. It awakens in them a sense of excitement and wonder through the ability to communicate with friends around the world from your loungeroom at home of from the saloon of a small boat at sea. A license is needed to do this since operating a ham radio requires selection of a free, complying frequency as compared to a marine SSB radio which has a simpler to operate, channel-based system. Ham radio enthusiasts need both technical knowledge and an understanding of the regulations to pass the licensing exams. Plenty of help is available to learn these skills and the rewards, especially for a "maritime mobile" operator are invaluable. 

A number of amateur radio (ham) maritime mobile networks operate around the world, designed to assist cruising yachts by providing check-in facilities, position tracking, weather and location data. In addition to this great service a ham can chat all day to other hams around the world (great if your family or friends at home are licensed) and he/she can send free email using the "winlink" system. SSB allows ship to ship and ship to shore facilities on a more or less commercial, per channel basis. Email over SSB using the commercial "Sailmail" system is also available at a reasonable price. 
Both systems require similar installation and equipment and the notes that follow apply to both. Some marine SSB radios also offer limited ham functionality at a price - so you can have it both ways!


The essential components are a radio (HF transceiver), antenna tuner , antenna and earth system. Modern mobile ham radios and some SSB, feature a control head separate from the radio as shown in the Icom 706MkIIG below. There are significant advantages in this arrangement, allowing a small panel footprint at the Navstation for the control head and an out-of-the-way location for the radio convenient for 12V power and antenna connections.

llywhacker has an Icom 706mkIIG - the control head mounts easily on a flat surface at the Nav table and the radio proper at the rear of this photo is mounted in the copper box shown in the photo below
For a "long-wire" antenna, the antenna tuner should be directly below the backstay or whip antenna under the deck and as close as possible to the earth system

An Icom AH4 antenna tuner - water resistant design for under deck mounting, usually at the stern under the backstay. Illywhacker is a ketch and uses the triatic stay as an antenna.


The aim of the installation is to ensure 99% of the power from the radio is radiated from the antenna. A boat floats on a perfect "rf ground", the sea so antenna systems are often designed in a 1/4 wavelength configuration. When such an antenna is tuned to the desired frequency (determined by its length and the ATU settings), the ground plane acts in concert to ensure all power is radiated from the wire - both are equally important. 
Most yachts find it easiest to use the backstay as an antenna. This requires 2 insulators be inserted, the lower one a metre or 2 above the deck to avoid radiation burns if human contact is made during a transmission.

The insulated cable leaving the ATU is passed through a waterproof gland in the deck, run via standoffs up the backstay and connected with an anti-drip loop to prevent water finding its way down the cable core.
Grounding is often easiest using an external "dynaplate" but much literature suggests connection with the ship's earth system. This is our preferred arrangement although this also introduces issues such as electrolysis and interefrence - try, measure and see!

A good installation in accordance with the sketch above will yield some amazing results - clear communications around the world sometimes - with few side effects to the performance of the yachts electrics/electronics. Adding more equipment such as a modem and computer for email, antenna switching, weather fax modems and so on are all part of the fun, especially when inadvertent coupling causes the auto-pilot to veer off course or the lights to flicker when transmitting! There are ways around all such problems and the ham and cruising community is always ready to help. I find this a fascinating topic and would be happy to share our experience with readers wishing to understand more.


Don't let the words "single sideband" scare you.  SSB is simply a type of radio transmission.  The military has been using "single sideband" for years to transmit message throughout the world.  Ham radio operators have been using "single sideband" for years on worldwide frequencies to talk to their buddies anywhere and everywhere.  There are enormous benefits to installing a Single Sideband radio on your boat.

With a Single Sideband radio you can:

1) Talk any other vessel ANYWHERE in the world, so long as they also have an SSB.

2) Contact shore stations such as private marine businesses, yacht clubs and rescue services. 

    You can even set up your own shore station to stay in touch with your business while FAR out at sea!

3) Send and Receive Internet e-mail from ANYWHERE in the world for VERY low cost.

4) Receive Weather Charts from ANYWHERE by connecting your computer to your SSB with weatherfax software.

At H.F. Radio we are intimately familiar with the details of our products and enjoy sharing this information with you.  Please continue reading to learn much more about SSB's and the various products we offer.  At every opportunity we attempt to provide you with links directly to manufacturers websites or other informational sites...Please explore them, BUT don't forget to come back to our site!!!  You won't find our great service coupled with fair prices ANYWHERE else!!!

Why Consider On Board Single Sideband Radio (SSB)

I have made a promise to the various family members and friends to remain in touch via eMail - even when I'm out sailing.  Now my problem is how to keep this promise without breaking the bank on communication equipment and services.  For the near future, I believe that Amateur SSB radio communication is the best way to go.  With SSB, I can communicate over a range of several thousand miles and this will clearly meet my needs.

SSB radio for eMail requires several major items of equipment - and all of them need to be as small as possible.

1) A Transceiver capable of SSB operation on the frequencies of interest and digital transmission modes
2) An Antenna
3) An Antenna Tuner matched to the transceiver model
4) A Radio Modem
5) A Laptop Computer

The guiding principle for equipment selection must include low cost, small size and low power consumption.

As a guess, a new commercial marine SSB installation with the hardware required for eMail (not including the laptop computer) will cost around $3,500 plus installation ($1,000 to $1,500 generally).  The commercial service contract will also have an operating cost of about $450 or more per year depending on how much you use the eMail.  By getting an Amateur Radio License, I hope to get this down to about $1,500 or less going the route of used amateur radio equipment - an added benefit is that there would be no significant operating costs and I will do my own installation which will save significantly

Commercial Marine SSB

In 1999, AT&T closed their Public Coast Radio Stations since they claimed that their continued operation was too costly and that other means of offshore communication such as satellite were available.  For the commercial marine segment (and private individuals with Fat Wallets), this is clearly true.  However, for the little guy, SSB is still a very good option.

As of now, there are still several smaller commercial Public Coast Stations in operation - the majority of which provide only SSB eMail service.  If the sailor needs to send business related eMail, then this type of SSB is the only option since Amateur Radio is forbidden to transmit business related messages.  Also, if obtaining an amateur Radio General Class License is not possible, then this is the only way to go.

The advantage to the commercial option is that you pay for a service and have a choice of providers (even if the list is small).  Also, the Marine Operator's Permit and Station License that is required do not require technical tests to be passed.  Since the operator permits are universally recognized, no special requirements exist when crossing international borders.

The main disadvantage of the commercial route is the limited selection and higher cost of the FCC Type Accepted radios that are required to operate in the Marine frequencies.   Even in the used market, these radios can cost two times the amount of an equivalent Amateur radio.  In addition, there are some significant fees associated with Commercial eMail services - both annual contracts (about $30 to$40 per month with a one year minimum contract) and additional usage based fees that can range up to $1.00 per message unit.  In this case a message unit is defined the smaller of one message or a block of 1000 characters (including control characters).  This means that a two page letter via eMail will cost $2.  Even with limited uage, this can add up to a fair chunk of change.

Amateur Radio SSB

In order to participate in Amateur Radio, a valid FCC license is required.  On December 30, 1999 the FCC announced a major restructuring of the License requirements.   Under the new rules scheduled for implementation on April 15, 2000, a General Class License will still be required for access to the frequencies in common use for long distance eMail.  Under the new rules, this License will require passing two written exams on rules, theory, practice, and safety of radio operation.  In addition, knowledge of Morse code is required and the operator must be able to send and receive at a speed of 5 words per minute (25 characters per minute).  Passing the written tests should require some study with a few good books since all of the possible questions on the test will be published for anyone to review - the Morse Code test will require more concentrated study with one of the many Morse Code Tutor programs available on computer.

Amateur radio is composed of a universe of dedicated hobbyists - many of whom also are sailors or pursue other mobile recreational activities.  In response, a network of Amateur stations have been established to provide gateways between the world of Radio and Internet based eMail. These are not commercial activities and the stations will come and go as time and the operator's interests dictate.  However, there seems to be enough interest in this activity to assure some degree of connectivity for the near future.

From an equipment standpoint, there are several manufacturers and a steady supply of relatively modern and less expensive used equipment on the market. However, Amateur Radio is licensed by each country and as an amateur operator crosses international borders, a new temporary operating permit application will be required in each country with a generally small fee being paid.  In the Bahamas for example, the fee is $6.00 - the permit is usually issued within a week or two and is valid for a period of one year.   In Canada, no application is required but in Mexico, an application is required and processing may take more than one month while the permit is only valid for six months in total (including procesing time).  In other  words, plan in advance!

My plan is to be in line as soon as the new rules go into effect and pass the examinations required to get my General Class License.  In the mean time, I will continue to scout the auction sites and Ham swap meets for the equipment I require.   Due to the transition plan between the old and new rules, I may take some of the examinations under the old rules in order to get a jump on the requirements.

Commercial Marine Radio Equipment

In order to use a SSB radio for Marine use, it must be type accepted by the FCC.   As of now, this limits the market to companies such as Icom, SGC, and SEA.   There are other high end providers but their equipment is out of sight for all but the large commercial vessels.  Some of these manufacturers also provide dual purpose units that are capable of both Marine and Amateur service.  In this capacity, they are really Marine radios that can transmit out of their assigned bands into the amateur frequencies - they are no where near as flexible in their operation as most Amateur Radio operators would like to see.

From what I have seen, the most desirable Marine radio would be the Icom M700-PRO model or the similar ICOM 710.  These models are available from West Marine and most other marine suppliers at a cost of about $1,100 to $1,600.  A matching antenna tuner (Icom AT130 ) is also required and sells for about $500

Amateur Radio Equipment

There are a significant number of companies producing Amateur Radio equipment for the 2 million or so amateur Radio Operators worldwide.  With a relatively large market, there is also a significant amount of used equipment available so this might allow cost cutting.  Since a driving force behind my requirements is to have eMail on my sailboat, I will need to concentrate on more modern equipment designed for low power consumption and digital transmission capability.  One additional requirement is that the receiver be general coverage so that receipt of SSB Weather Charts is possible.   For those interested in listening to the international broadcast frequencies, the older Amateur radio tranceivers supported AM reception which is sometimes easier to use than trying to tune an AM signal with an SSB receiver.

My first amateur radio consisted of an ICOM 735 purchased used.  This worked well but was physically large and consumed more power than I would have liked to use.  At it's minimum settings, the unit transmitted at 10 watts and I found that this was more than I needed.  I then went looking at alternatives and now, my station consists of an Elecraft K2 transceiver with the internal SSB module and antenna tuner options installed. 

The Elecraft K2 was selected due to it's low power consumption and high quality receiver functions.  This radio is only available in kit form from the manufacturer but the process of building the radio is well documented.  It took me about two and one half weeks to complete - and that was while living aboard the boat.  Conventional wisdom says that you need 100 watts of power to communicate via SSB - NOT TRUE.  I have never had a problem exchanging email with land based stations using only the 5 watts that the K2 supports in digital modes.  In fact, I have been successful with less than 2 watts over a range in excess of 1,000 miles.

Radio Modem

With respect to the Radio Modem, the top of the line is the Pactor II from SCS.   At a price of about $1,000, this would not be a realistic selection for my purposes.  Even the Pactor IIe economy model sells for almost $650 and is too new to be found on the used market.  Since money is tight, I should start with older technology such as the Kantronics KAM Plus or AEA PK232.  With upgrades available from the manufacturer, these units support the Pactor I but not Pactor II protocol.  Ebay seems to offer a number of these at any point in time but the price of a used unit with the additional costs of upgrading to the current version firmware will bring the total to $250 or more.   Also, even with the upgrade, these units are still only capable of Pactor I operation and not the much more efficient Pactor II.  Furthermore, the software of choice for eMail over amateur radio does not support all brands of modem so this will impose additional limitations.

It seems to me that efficiency is the killer in this equation.  I really don't want to spend the money for the Pactor IIe unit, but since it operates about 5 times faster than any modem using Pactor I, I really don't have much choice.  The electricity supply on a small boat operating off a solar panel system is the deciding factor, if I can cut down on electricity consumption with a better modem, this is the best solution despite the higher initial outlay from my coin collection..

I will not minimize the complexity of this operation.  Getting an Amateur Radio, a Radio Modem, and a laptop computer to operate together is not "Plug and Play" - it is not an  easy task - and then it must still be able to communicate with a similar setup several hundreds of miles away.  This will take time and effort to establish the connectivity. I followed the hardware installation recommendations given on the Airmail 2000 software site - including the use of clip on ferrite chokes on all interconnecting lines (radio,  radio modem, and laptop computer)

Antenna Considerations

A sailor can have the most expensive SSB radio, the best Radio Modem, and the best Laptop computer to connect them for digital communication and still not be able to communicate across the anchorage or out of shouting range if the antenna system is poorly designed.  I have no intention of going into antenna theory here - I just want to describe the options I have considered and then describe my starting point.

Conventional wisdom says that a good SSB antenna on a sailboat is VERY difficult and EXPENSIVE to install. The experts will ramble on at great length about the requirements for a counterpoise (ground plane), the cost of backstay insulators, special weatherproof automatic antenna tuners, and special cables to join the various pieces. The experts are absolutely correct - but only if you want access to SSB transmission at any and all frequencies both at anchor and while under way.  However, if you only want to use SSB transmission every few days while at anchor - is it still difficult and expensive - NO!!!

The Expert's Antenna Choice for a Sailboat

There are several commonly used antenna configurations for a sailboat - most users install an insulated backstay for their antenna with some others installing a vertical whip (23 feet tall minimum).  In either case, the major factor that determines good long distance operation will be the installation of a very high quality ground plane (also called a counterpoise) for the antenna.  These antenna types also require a sophisticated (and very expensive) antenna tuner to operate correctly.

For either of the above antennas to operate on the many different frequencies of the Marine and Amateur services, the antenna must be at least 23 feet long and the antenna tuner must be connected to a ground system composed of copper foil radials that are as long as possible and have as much surface area as possible.  Some experts suggest that a minimum of 100 square feet of copper foil is necessary for good operation with a backstay or vertical whip.  One thing is essential and that is to keep the antenna tuner as close to the antenna and the ground plane connections as possible (no more than 3 feet).   If copper foil ground planes are to be constructed, the recommendation is to make each of them at least 20 feet long and 3 inches in width (5 sq ft at a cost of about $25) - as many of these radials as possible should be installed.  Another approach is to use wire mesh screen (copper if possible) as a ground plane.

This arrangement is the most flexible and will allow operation under all conditions (as long as your rigging stays intact).  The insulated backstay is expensive ($200 or more for the two insulators) and the insulators are a weak point in the rigging design. Experts recommend replacing the insulators more frequently than any other part of your rigging.   The antenna tuner (about $500) will match your backstay to all frequencies without damage to your transmitter - but the efficiency of transmission may be less than 10% (150 watts from the transmitter but only 15 watts out via the antenna with the rest of the energy showing up as heat in the tuner and ground losses).  Modern antenna tuners will match a transmitter to a length of string soaked in salt water - but this does not mean you will be efficient at transmitting.

The total installation may well take several man days and require access to every nook and cranny of the boat - a REAL mess!!  Also, on a Flicka, the length of the backstay and the length for installing counterpoise radials is minimal at best.

My Non-Expert Antenna Choice for a Sailboat

My use for SSB radio is as a means of communication with friends and family - digital transmission for eMail will be the major mode of operation.  This means that my needs are very limited and I will only use the system at anchor and not while underway.  As a coastal sailor, a good VHF system is much better for emergency and routine marine communication.  At anchor, I can raise a temporary shortwave antenna into the rigging, get my eMail, and then put the system away.

The design of high quality temporary antennas of this type are well understood and can they can be produced inexpensively.  Amateur radio operators have been using them for years on Field Day and other emergency preparedness tests.  Most automated communications is limited to a narrow range of communication frequencies with world wide coverage potential (30 and 20 meter wavelength).  For the frequencies I need access to, an efficient 1/2 wave length dipole antenna will range from 46 feet long down to 33 feet long (30 and 20 meter wave lengths) as end to end dimensions.  Dipole antenna's consist of nothing more than two sections of stranded copper wire (insulated AWG 14 will do) with an insulator in the middle of the two sections and on both ends - the whole thing looking like a clothess line.  The connection to the transmitter is made at the center (called the feed point) - generally with high quality coaxial cable.  Physically, this antenna can be aranged in two ways - as an inverted "V" with the center raised to the top of the mast and the ends suspended by their insulators fore and aft, or as a "sloper" with one end at the mast head and the other end suspended from the pushpit.  The single largest advantage of this arrangement is that NO COUNTERPOISE IS REQUIRED!!

There is no free lunch, while efficient, this setup means that you should construct one antenna dedicated for each band of operation.  Also, the antenna is somewhat directional with very little radiation off the ends of the antenna (fore and aft).   If you sailboat is swinging significantly at anchor, a contact might be difficult to maintain unless you use two anchors.  Using the Dipole antenna approach is especially attractive to a salt water sailor since the electrical properties of salt water make it an ideal reflective ground for radio frequencies.  This is why long distance transmission of radio waves over salt water has long been known to be very efficient.  Additionally, that lonely anchorage also is missing much of the the man made  electrical interference that radio operators need to spend so much effort at overcoming.

There is an alternative arrangement of the inverted V dipole antenna that is even simpler to construct for use on a small sailboat.  This is the Resonant Feed-Line Dipole antenna and details on it's design are available via the internet.   I'll start with this system since it is so easy to set up.

Another choice for antennas is the Pro-Am Valour (Ham Stick) series of antennas.  At the frequencies I operate for email, these antennas are efficient and easy to set up.  The mount is attached to the pushpit and the toe rail of the boat is ties electrically to the pushpit to act as a radial counterpoise.  Additionally, a section of ten feet of tinned braided copper cable is run to the saltwater whenever this antenna is in use

SSB Weather FAX Service

Once a good quality Single Sideband receiver (Unfortunately, the Elecraft K2 only covers the Ham bands and receipt of weather FAX is not possible with this radio.) and computer are on board, a logical extension is to use the equipment to receive the latest weather information.  The Coast Guard has a broadcast schedule of weather products for mariners that includes a number of charts as well as text and voice transmissions of weather reports.  A schedule of transmission frequencies and times is available on the web.   Broadcasts that cover the area of interest for me (Florida with points south and east) are issued from Belle Chase LA.  Currently (Spring 2000), they use frequencies of 4317.9, 8503.9, and 12789.9 with the schedule of transmissions starting at 00:00, 06:00, 12:00, and 18:00 UTC - each scheduled transmission block lasts just over 2 hours.  A complete broadcast schedule is also issued at 06:30 and 18:30 UTC in HF-Radio FAX format.   To receive the broadcast, tune 1.9 KHz below the listed frequencies using UPPER sideband.   Remember that atmospheric conditions, distance from the transmitter,  and time of day will determine which of the listed frequencies you will be able to receive from your current location.  Don't expect these weather maps to be in extreme detail like your local TV news - they are general in nature but will give you a good idea of the conditions you are likely to encounter when you are out of range of the usual sources of broadcast weather data.

Knowing when a Weather FAX chart will be transmitted won't help if you can't decode the chart to display on your laptop computer.  For occasional use, I suggest JVComm 32 (In January 2000, the most current version was 1.0 and the registration fee was $68).  This shareware program will use the Soundblaster compatible hardware on your Windows 95 or higher laptop computer to decode the transmission and display the received chart on the computer screen.  Under some conditions, a direct connection between the computer and radio is not even necessary since the decode process can use the computer's microphone input if the computer and receiver are close together.  Be sure to test the software using the demo download on your computer system before actually purchasing it.  The current version software (Version 1.0) requires a download of about 3.5 MB.  If you need access to weather maps more frequently, the dedicated HF radio modems are much better and more reliable.   JVComm32 supports the Pactor IIe modem directly so there is no need for the sound card.

The Coast Guard stations also broadcast weather information in English (using a computer generated voice that is sometimes difficult to understand) on the same frequencies.  There are other weather broadcast formats available in text form (a radio modem is required) - information is on the links page.  While we are on the subject of Time - do not neglect to set your watch using the WWV broadcast on a frequency of 2.5,  5.0, 10, 15, or 20 MHz.  This is also a nice way to check the calibration of your receiver's frequency display.

Sailboat SSB Directionality Effects 

The Hamstick antenna described above is normally expected to radiate it's signal uniformly in all directions.  The caveat is that this radiation pattern is expected when the antenna is mounted in the clear and away from any other metal objects.  Unfortunately, a sailboat is far from a clear location for an antenna mount.

Computer antenna modeling shows that the 25 foot mast on a Flicka is the perfect height to act as a passive antenna element on frequencies of 14 MHz (20 meters) and above.  Depending on the frequency in use, the mast will function as either a director or a reflector.  This means that the majority of the radio signal will be beamed either off the bow or off the stern - again the direction will be frequency dependant. 

Since I use frequencies in the 30 meter band (around 10.125 MHz) most often, I do not experience this directionality effect.  However, the computer models clearly show that I should avoid higher frequencies.

Using a Terminal Node Controller (‘TNC’) with laptop and SSB Radio: 

 A TNC is the equivalent of a SSB ‘modem’ as it allows the digital output of your computer to be transformed into the analog signal sent – and received - by your radio.  (I hasten to point out before going further that an entire book could be written on this subject)!  There are experienced cruising sailors who think the $600-900 U.S. cost of the TNC can be better spent elsewhere since one of its main benefits – receiving email via the SSB radio – can be accomplished in many other ways when ashore, though not at sea.  Pocketmail, Cyber Café, direct ISP connection are all examples.  And to be fair, another reason some steer clear of using a TNC is that there’s a fairly steep learning curve initially, although you can rely on a vendor like HF Radio ( to help you through this phase.  So…if it’s pricey, requires a later model SSB radio in order to work properly, mandates the placement and use of a laptop somewhere on the boat, and isn’t intuitively obvious to initially use, why do I have it on my ‘Best Mods’ list?  Here are the ways we’ve benefited, along with some sources of information and related comments. Hopefully, I’m stating all this in normal English at the expense of using more correct technical jargon, as one problem most of us have when starting to climb the learning curve on TNC/SSB use is the language specific to this topic.

Sailmail refers to a world-wide non-profit commercial system which offers a gateway service to the internet; vessels use marine equipment/frequencies with only marine licensing required; daily connect time is limited to 10-15 mins.; see for more info

** Winlink refers to a world-wide system of shore stations which serve as gateways between vessels using Amateur Radio equipment/frequencies and the internet; daily connect time can be up to several hours if connecting with multiple shore stations; see for more info

Perhaps it sounds mundane, tedious or even counter-intuitive to be receiving email offshore; isn’t that one of the things we’re trying to escape?  Here are some uses we made of our TNC on our last passage, none of which in retrospect we would choose to do without:

  • Digital-quality weather products provided routinely when we connected with Winlink; the specific products were selected before the passage began and then sent to us using an automatic ‘request and receive’ feature.  As our position changed over time, we rotated out some products in favor of newer one; free service
  • When we lost access to a regional forecast service due to propagation, the same information was emailed to us by a net controller; free service
  • Like most everyone our age, we have both older, frail parents and a broad circle of friends; thanks to the TNC, they were all able to ‘come along for the ride’ via the occasional group or individual emails.  It’s hard to overstate the value of maintaining relationships at home when off on a journey to which others find it difficult to relate; free service
  • At several points, we supplemented offshore forecasts with local, inshore forecast information by copying the Navtex broadcasts on 518 and 490 kHz; especially helpful as we approached the English Channel; free service
  • Special navigational aid changes and also recovery work with an exclusion zone were also announced on Navtex broadcasts; free service
  • Although it’s available using multiple means, our TNC downloaded weather fax transmissions from Germany, the UK and U.S. and, provided the laptop was running and radio left on, it did so automatically – a big help for a short-handed crew; free service

If this is of interest to you and you’d like a “hands on” experience in using this software, download Airmail or Sailmail and play with it on your own computer.  If you’re more serious and would like the “hands on” experience to include understanding how to select the right products, set up an HF rig on your boat, and use these TNC-based programs, then consider attending the annual SSCA Gam held in mid-November in Melbourne, Florida.  The players who created and now operate these services, along with the key software developers who make it all possible, are all in attendance and conduct an all-day, hands-on seminar series.  And the cost – for the entire 3-day Gam – is peanuts.  It’s the best single resource I know of for cruising sailors who want to better understand this whole arena of products, skills and capabilities.


RTTY was first introduced to me in 1958-9. The UK had not used this mode before although there were plenty of commercial RTTY stations all over the short wave bands. Not much attention was paid to them, as it was not looked upon as an amateur form of communication.

One day Bill, G3CQE, received a phone call from "Doc" Gee, G2UK. He asked if there would be any interest in looking at some old Creed 3X teleprinters. There was some local interest, and four of us made our way to Lowestoft to investigate. The outcome was that three machines made their way to Norwich. Experiments on local-loops followed and eventually Bill, G3CQE and Doc made the first contact. Talking to Jim Hepburn, VE7KX, on CW, Bill found that there were several stations active on HF RTTY. There was an attraction in the sound of the mode for me, I suppose being a musician helps here, as the sound is quite musical. I well remember the confrontations we received from AM users of the bands telling us to "Stick our jungle-bells". However, SSB was treated with much the same disdain from the old stalwarts who did not want their bands changed! Notwithstanding this, the interest mushroomed and the rest, as they say, is history!

We managed to obtain a couple of Creed 7B machines, and were off on HF. Interfacing to the then used home-brew rigs was fairly straightforward, with a small variable across the VFO adjusting the frequency shift. This, in those days, was 850Hz. In fact it was not even Hz, it was still 850kcs ( in fact I still think of it in those terms! ) Bill, G3CQE was the first UK amateur on HF RTTY and I was not far behind. Interest grew rapidly and visits to junkyards followed on a regular basis, looking for the much-valued Creed 7B's. Many machines came onto the scene after this, and most amateurs would have given an extremity or two in order to own a 28ASR. These were considered the ultimate machine. There were few about, and I never did get to own one. I ended my "noisy" days with a Model 19 Set, the full table! Contests were laid-back affairs, most RTTY-ers were known by name, and we took time to exchange niceties. Now it is much more clinical, even to the extent of debating whether to send a Carriage Return at the end of an exchange or to leave it out and save time. Personally I think we will lose something if we take this too far, but then I am a G3.... 
So much for the history. Let us now look at the scene as it is now:

RTTY is a fun and easy mode to operate, but there are a few things, which may be puzzling to the newcomer. However, in modern technology, most of the interfacing is done with software, and very little can go wrong. It might be a good idea, however, to understand a little of the fundamentals.


A RTTY transmitter sends out a continuous carrier that shifts frequency back and forth between two distinct frequencies. There is no amplitude modulation, only a pure carrier similar to CW with the addition of a frequency shift. The lower RF frequency is known as the SPACE frequency and the upper RF frequency is known as the MARK frequency. The difference between the two is known as the SHIFT. For amateur radio, the SHIFT has been standardized at 170 Hz. It is customary to refer to the MARK frequency as the frequency you are operating on. For example, if you say you are transmitting on 14080.00 kHz, that means your MARK frequency is 14080.00 kHz and your SPACE frequency is 170 Hz lower, or 14079.83 kHz. While 170 Hz is the standard shift, sometimes you will find stations using a shift of 200 Hz, but don't worry about it. MMTTY will copy either shift automatically, and the other station will copy your 170 Hz shift as well. It is not that critical. There is also a contest using lower shift only, quite easy to do with the software tweak.


You will often hear the terms FSK and AFSK when talking about RTTY. FSK means Frequency Shift Keying and AFSK means Audio Frequency Shift Keying. Here is an important point: Regardless of which method is used, the RF signal sent out over the air is identical. MARK is always the higher RF frequency and SPACE is always the lower RF frequency. The station receiving the RTTY signal cannot tell any difference at all. The difference is the way your transmitter generates the RF signal.

With FSK, your transmitter receives a simple on-off signal, which causes the carrier frequency to shift back and forth. If you use MMTTY, one of the most commonly used software programs for RTTY, the on-off signal will come from a COM port on your computer. Other stations that do not have a soundcard program like MMTTY would use a separate box called a TNC (Terminal Node Controller). The TNC does the same job that MMTTY does with your soundcard. FSK is simpler, easier and more foolproof than AFSK and is highly recommended if your transmitter supports FSK input. Check your owner's manual if you're not sure.

Since not all transmitters support FSK input, there is another method available with MMTTY, and that is AFSK. AFSK can be used with any SSB transmitter. AFSK is a bit trickier to set up and use, but when it is done correctly, it works just as well as FSK and will transmit a perfect RTTY signal. Also, AFSK can do some things that FSK cannot, such as Automatic Frequency Control (AFC) of the transmitter. 
To operate with AFSK, you put your transmitter in the SSB mode instead of FSK mode, and you inject an audio signal into the microphone input (some transceivers have a rear connector for data input). When you transmit, MMTTY causes your sound card to put out a pair of audio tones that cause your transmitter to send the required RF output. The tones are two sine waves but the frequency and amplitude of the tones is critical. 

Let's say you want to transmit on 14080 kHz, as in the previous example. Remember, your MARK signal has to be on 14080 kHz. With your transmitter in the LSB mode (Lower Side Band), whatever frequency goes into the microphone input will be subtracted from what your dial says and be transmitted on that frequency. For example if your dial says 14080 kHz and you put in a 1000 Hz audio tone, your transmitter will put out an RF signal at 14079 kHz, exactly 1000 Hz lower than your dial. So in this case, if the 1000 Hz represented your MARK signal, you would have to set your transmitter to 14081 on the dial, and your MARK signal would be transmitted on 14080, just as you wanted. The SPACE frequency will be transmitted 170Hz lower, on 14079.83 kHz. The audio tone that will give you 14079.83 is 14081 minus 14079.83, or 1170 Hz. So the MARK audio frequency is 1000 Hz and SPACE is 1170 Hz.

There you have the basics of AFSK. MMTTY generates the two audio frequencies and your transmitter converts them into two RF frequencies. For technical reasons related to harmonic generation, audio frequencies of 1000 Hz and 1170 Hz are NOT recommended. They are used in this example just to keep the math simple. The recommended audio frequencies are 2125 Hz for the MARK audio frequency and 2295 Hz for the SPACE audio frequency. Making the frequencies higher like this will reduce any second harmonics that might be generated in your transmitter. At one stage lower tones were used and this very problem caused a MAJOR problem on the air.

You may have noticed the SPACE audio frequency is higher than the MARK audio frequency - just the opposite of the RF frequency you actually transmit. This happens because you're using lower sideband. If you happen to forget and set your transmitter to USB instead of LSB, two things will happen. Because your MARK and SPACE are now reversed in your receiver, any RTTY signals you hear will not print correctly. All you will see is random characters that make no sense at all. The other thing is that YOUR transmissions will also be nonsense to the other guy, so just remember - always use LSB. In the real world of course, sometimes USB gets selected accidentally. This is why MMTTY has a button marked REV. When you have a station tuned correctly but all you see is nonsense printing, click on REV and your transceiver will be reversed. Now you can print the other fellow and tell him he is "upside down", as it's commonly called. After he reverses himself, just click REV again and you will both be back to normal.

Note: By default when using AFSK, REV reverses both your receiver and transmitter. If you want REV to reverse only your receiver, go to Option/Setup MMTTY, click the TX tab and click "Disable REV". When using FSK, REV reverses only your receiver. If you want to reverse your transmitter and receiver with FSK, your transceiver should have a way of doing that. 
Also, you should know that in some parts of the world, especially Europe, the standard is to use USB instead of LSB. This works fine as long as you also reverse the MARK audio frequency and the SPACE audio frequency. MMTTY defaults to LSB, and it is recommended to leave it there, even in Europe, since your signal will be identical. If you prefer to use USB, leave REV on all the time. This is no big deal on most modern transceivers, as the memories can be set up in such a way that modes such as RTTY will come up correct each time when selected via the memories. 

The really critical part about AFSK is the amplitude of the signal fed into the microphone connector (or rear panel connector), together with the microphone gain setting. You must NOT overdrive your transmitter or spurious signals will be transmitted. In general, keep the audio drive low enough that your transmitter does not generate any ALC voltage. Never try to drive your transmitter to maximum output. Around 80 to 90 percent of maximum is about right. Consult your owner's manual for more information on how to do this. If you ever hear a station at two or more frequencies at the same time, the cause is almost always overdriving. None of this applies to FSK, of course. With FSK, you can run full power and not worry about overdrive.


RTTY uses the Baudot code, invented before radio even existed, and still widely used throughout the world. The Baudot code uses data bits to represent letters, numbers and punctuation, much like your computer does. Unlike your computer, which uses eight bits for each character, the Baudot code uses only five, plus a start bit and stop bit. Using fewer bits is good because it speeds up transmission and reduces the chance of errors, but there is a complication. Five data bits can only represent 32 different characters. Since there are 26 letters in the English alphabet plus ten numbers, plus some punctuation, 32 different characters is not enough, even if you only use capital letters, which Baudot does.
Mr. Baudot could have chosen to use six data bits or even more, but he found a better solution. He reasoned that most of what would be sent would be letters rather than numbers or punctuation, so he assigned all the letters to the basic 32. He then had six characters left over and he did a very clever thing with two of them. He made one of them a FIGURES SHIFT and another a LETTERS SHIFT. The way it works is this: When sending one of the basic 32 characters, nothing special happens. But when a number or punctuation is to be sent, a FIGURES SHIFT character is sent first (it's a non-printing character - you won't see it on your screen).
Whatever follows will still be one of the basic 32 characters, but the receiver will interpret it differently. For example the letter Q uses the same five data bits as the number 1, but when the receiver gets a FIGURES SHIFT first, it prints the next character as a 1, not a Q. This continues until a LETTERS SHIFT character is received, at which time the receiver goes back to "normal" printing. All of this shifting is done by the system - there is no key marked LETTERS SHIFT or FIGURES SHIFT. It's all automatic and you will scarcely notice it happening. 
In fact, the only reason to mention it at all is because we are using radio instead of wires, and radio is susceptible to interference from various sources such as lightning static, man-made noise, etc.
If a burst of static should happen to wipe out a LETTERS SHIFT or FIGURES SHIFT character, the characters following will not print correctly until another LETTERS SHIFT or FIGURES SHIFT is received. For example, suppose you are sending a signal report of 599, but a burst of static wipes out the FIGURES SHIFT character. Instead of printing 599, the other fellow's computer will print TOO. TOO is exactly the same as 599, without the FIGURES SHIFT. We all got used to interpolating "shift" transmitted reports and serial numbers in the early days!

Using MMTTY however, there is an easier way to read wrong-shifted characters. With the right mouse button, just click on the word and it is instantly changed to the opposite shift. Right-click again, and it's shifted back. Easy as can be.


When the bands are nearly empty, you can use practically any receiver bandwidth with good success. Your SSB filters are probably between 2.1 and 3.0 kHz wide and as long as no other stations are nearby, copy will be fine. For optimum performance however, less bandwidth is better, in fact MUCH better. 170 Hz shift RTTY only needs about 250 Hz for proper copy. If you don't have a 250 Hz filter, 500 Hz will do pretty well, but anything wider than that will not be satisfactory in the long run. Further discussion on this subject can be found elsewhere.
For amateurs, the ARRL handbook is a good source. Depending on your transceiver, you may or may not be able to use a narrow filter for RTTY. Some of the less expensive transceivers do not have an FSK mode, and also are unable to select a narrow filter while in the LSB mode. Using an outboard audio filter between the speaker output and the soundcard input can make some improvement, but unfortunately, that will not prevent a strong adjacent signal from causing the receiver's AGC circuit to reduce gain, often to the point where the desired signal disappears. The best solution is to upgrade to a transceiver that has an FSK mode built in, AND which allows you to select a narrow filter while in that mode. 

Modern DSP filtering helps enormously here and using both on-board and external DSP filtering can be very useful.


It's easy to remember the band plans for RTTY. Most activity will be found between 80 and 100 kHz up from the bottom edge of the band, except for 80 meters, which goes an additional 40 or 50 kHz higher, and 160 meters. 160 meter RTTY activity is rare, but when found, it is usually between 1800 and 1820. Avoid the CW DX window between 1830 - 1840. At present, there is not much activity on the WARC bands, although 30 meters can be active at times. 
Here is where you will find most of the RTTY activity:
80 meters: 3580 - 3650 (3520 - 3525 in Japan) 40 meters: 7080 - 7100 
in the US (see note below) 30 meters: 10110 to top of band 20 
meters: 14080 - 14099 (avoid the beacons at 14100) 15 meters: 21080 
- 21100 10 meters: 28080 - 28100
RTTY allocations for 40 meters vary greatly all over the world. In the US, RTTY is permitted between 7000 and 7150, although most US activity is between 7080 and 7100. DX activity is often found between 7020 and 7040. As you see, RTTY in the USA on 40 meters covers half as much again as we have in total bandwidth for ALL modes! About time we had another 400kHz of allocation on this band.


Chasing DX on RTTY is highly popular with the RTTY crowd. As you might guess, 20 meters is the premier DX band for RTTY, and most rare DX stations and especially DXpeditions operate on 14080. Just like with CW or phone, if the DX is calling CQ and getting no answers, you can feel safe in calling him right on his frequency. If things are busy however, he will often work split, which means you should call him on a different frequency, usually 2-10 kHz higher. He will say "up 2-10" or something similar at the end of his transmission, and that's your clue. Your transceiver owner's manual will explain how to do "split". Split operation in the early days was not possible on any mode! Now it is common practice and even on RTTY quite easy to do.


RTTY contesting is a passion with a lot of operators. There are about a dozen major RTTY contests each year and when they are on, the bands will be full! Even if you don't care to compete, it's a great way to pick up new states or countries. Many of the rare DX stations are serious contest operators. A list of RTTY contest times and rules can be found on the web at: or
Contesters are in a hurry, of course, so please don't send your name, QTH or anything except what is required by the contest. Plenty of time for chatting after it's over.

If you are really serious about contesting then take a look at WRITELOG. This program, coupled with MMTTY is one of the most commonly used combo's on the bands today. There are numerous RTTY software programs, all running from the sound card on the PC. If you look at the RTTY site of AA5RU, you will find lots of help here, together with suggested downloads etc.


For your first time on RTTY, try the 20 meter band. 20 has the lion's share of RTTY activity and you can usually find someone, day or night. Try calling CQ between 14080 and 14087 kHz. A typical RTTY CQ would go like this: 

Practically all RTTYers add the "PSE" at the end. Some will add their name and QTH, some will add the time and date. You'll find a lot of variety and it's all ok - just get on the air and try it out! Again, with all the modern software, you can construct macro's ( we used to call them "brag tapes" due to the fact that we had to make a punched tape of something we wanted to use over and over again! ) to hold constantly used exchanges.
If you're familiar with CW procedures, you'll be fine with RTTY. RTTY'ers use most of the Q-codes, as well as DE, K, KN, and all the rest. And if you accidentally find yourself "upside down", don't get embarrassed - we've all done it! RTTYers are some of the nicest people you'll ever meet, and things like jamming and profanity are almost unheard of.


In spite of the newer digital modes like PSK, Pactor, G-Tor and others, RTTY remains the favorite of contesters and DXers alike. RTTY does not use error correction, handshaking, or synchronizing, all of which slow things down. When quick back-and-forth exchanges are important, RTTY is the mode of choice. Roundtable discussions and nets, which would be difficult or slow with other modes, are a natural for RTTY, and RTTY is likely to be around for a long time to come. I hope you enjoy it and look forward to talking to you on the green keys! Oh yes, another leftover from 50 years ago. ALL teleprinters had green keys. I suppose I should say - See you on the "

A Pactor Primer

This document is intended as a guide for the mobile ham who is new to the world of message forwarding via the ham radio HF Pactor network. It is written by the author of the AirMail personal mailbox program, primarily for cruising sailors and RV travelers that want to stay in touch via amateur radio and email. Subjects covered include advice on equipment selection and installation, getting started with the AirMail program and getting connected to the Pactor network. The last section also covers doing it the hard way, using a dumb terminal program.

The biggest problem with getting started with Pactor is documentation. The Pactor controllers all come with thick manuals which cover a multitude of operating modes, but by the time you painfully extract the part that is relevant to Pactor you find the documentation to be pretty thin. Our advice is to treat the controller manuals as highly valued reference documents, sort of like unabridged dictionaries, and don’t attempt to actually read them unless absolutely necessary.

A further note on this document: Parts of it are full of fluff and can be skimmed quickly, but when we get to the step-by-step instructions on how to get your station on the air, then you need to slow down and read each word carefully.

Overview of the Network
Sending digital communications over radio is nothing new, but recent advances in technology and software have made it easier than ever before for mobile hams to stay in touch via ham radio. Email is almost universal these days, and is ideal for exchanging messages between mobile hams and their contacts at home. All that is needed is some method to get messages to a fixed station and from there to the internet. Thanks to the efforts of a bunch of dedicated system operators (sysops) and a few software developers, the pieces are all in place.

In order to exchange email messages with the folks back home, you will need a suitable radio setup to access a Mailbox (MBO) station via HF radio, and your contacts will of course need email access (you don’t need an account yourself). While there are VHF and satellite packet stations in use, most long-distance traffic is sent via HF Pactor stations and that is what we are going to focus on here.

There are literally dozens of HF MBO stations world-wide, most running the WinLink software package originally written by Vic Poor W5SMM and rewritten and developed by Hans Kessler N8PGR. WinLink stations are designed for automatic message forwarding, either to other WinLink stations via Pactor on the HF bands, or via the VHF packet network. The real breakthrough for mobile users to be able to keep in touch with the folks back home was the development of internet email gateways, and many WinLink stations now also operate internet gateways using the NetLink software package developed by Jim Jennings W5EUT.

Pactor is a method of sending digital information via radio, and was developed around 1990 by a small group of German hams who formed the company SCS. Pactor is an Frequency-Shift Keying (FSK) based system that incorporates longer blocks than the earlier Amtor system, robust error checking and automatic switching from 100 baud to 200 baud when conditions permit. The first Pactor controller was developed by SCS and the protocol was adopted by most other manufacturers of TNC's (Terminal Node Controllers, or radio modems), but often without the analog memory error correction scheme developed by SCS.

The Pactor team at SCS went on to develop Pactor-2, a two-tone phase-shift encoding (PSK) scheme. Their Pactor-2 controller is the PTC-II, with the modem implemented by a powerful DSP (Digital Signal Processor) chip and incorporating a fast 32-bit microprocessor to move the data. The original Pactor mode is also included (and in fact Pactor-2 operates as a "turbo" mode once contact is established via Pactor). Amtor, RTTY, Morse and weather fax modes are also provided, plus plug-in options for VHF/UHF packet.

A message on the digital ham network looks a lot like an email message, with a "From" and a "To" address, a subject line and a message body. Addresses are hierarchical and geographic. For example KE6RK@OE4XBU.AUT.EU indicates station KE6RK who can be reached at mailbox station OE4XBU in Austria in Europe. In Theory, a message can be entered into any BBS or MBO station, addressed to any other, and will get there by whatever route the MBO stations decide. Similar to email, the message is not generally delivered to the end user automatically, they must connect to the BBS or MBO station and collect it.

Passing messages between the ham radio network and the Internet requires a gateway between an email service and a ham radio MBO. Each message must carry two addresses, one for the ham network and a second one for the internet. The NetLink program handles polling the email server, reformatting the messages, and handing them off to the WinLink MBO program. There are limitations on the messages that can be handled, due to the relatively low bandwidth of the ham radio network and the regulatory limitations associated with ham radio communications. For ordinary email messages the bandwidth is not a problem and messages up to 5-10KB are commonly forwarded, and longer messages are possible with direct links to certain gateways.

The regulatory issues result from the international agreements that grant amateur radio some prime HF real estate, on a non-compete basis with commercial carriers. All of the various national regulatory bodies have implemented prohibitions on commercial messages, which in the U.S. prohibits any communication in which either party has a "pecuniary interest" (Part 97.113 of the FCC regulations, revised in 1993). So you can order a pizza via ham radio as long as neither party works for the pizza parlor. This language applies to U.S. hams operating /MM in international waters also, but different language may apply in other countries.

A second issue is non-ham third-party traffic, that is messages originated by or addressed to someone who is not a ham. For mobile hams in international waters or connecting to a U.S. MBO there are no restrictions and messages may be freely passed, but in other countries other rules may apply so it pays to check.

Choice of Equipment

The only difficult part of setting up a Pactor station is the variety of equipment that is available, none of which uses compatible connections. This means that cables need to be made up especially for each installation, which is the number one source of problems. (Number two is figuring out the correct transmit frequency).

Three components are needed to set up a Pactor station: a radio transceiver (and antenna), a data controller (also known as a terminal note controller or TNC), and a computer with some appropriate software. The controller is the only specialized piece of equipment, and is essentially a radio modem, similar in concept to the ubiquitous computer modem used for telephone connections. The controller generates the audio signals that are sent via the radio transmitter, and decodes the incoming audio signals from the radio receiver. So the primary connection between the controller and the radio is two audio signals (audio in and audio out), plus a PTT (push-to-talk) signal to tell the radio when to transmit.


Transmitting and receiving digital signals is similar to voice, and most modern SSB radios will do the job just fine. Ideally, the audio signals to and from the controller will be line-level (500mv) signals to a rear-panel connector, allowing the radio to be interchangeably used for digital and voice communications. Some older radios do not provide a rear-panel "accessory" connector, however, and the speaker and microphone connectors must be used. The audio level from the speaker jack will be adequate (although the volume cannot be turned down too far), but the controller's normal transmit audio may overload the microphone jack. Depending on the controller there will be a some way to reduce the transmit level if required.

The second issue is the transmitter's ability to transmit a continuous full-power signal without melting. Again, most recent transceivers can do this without a problem, but some older transmitters will have to be operated at a reduced power setting. This is generally no big deal, as even 25 watts is enough when conditions are good and many /MM's (Maritime Mobiles) routinely operate at 25 or 50 watts just to save the poor batteries.

Two less important issues relating to the transceiver are filters and a TCXO. A narrow-band (500 Hz) filter can be handy for reducing interference on the sometimes-crowded ham bands, but the controllers themselves are very good at ignoring adjacent-channel interference. The only time it becomes an issue is the rare case when a strong adjacent signal activates the receiver's AGC and reduces the level of all signals. Bottom line, if you have a narrow filter that works in SSB mode then use it, otherwise don't worry about it.

The TCXO issue relates to the accuracy of the transceiver's crystal oscillator. With digital signals operating with only a 200 Hz frequency shift, transmitting and listening on the correct frequency is a significant issue. Without a temperature-controller crystal oscillator (TCXO), a typical ham transceiver will drift 50 Hz or more as it warms up. This is not enough to be detectable on a SSB voice transmission, but for a digital connection would be significant. Pactor will operate up to 100 Hz off frequency but is happier (fewer errors) if within half of that, and Pactor-2 needs to be within 50 Hz. If a TCXO is available for your transceiver, then we would recommend installing it.

The Controller:

There are a number of controllers or TNC's on the market, although the SCS PTC-II and the Kantronics KAM+ are the most popular with mobile users (and currently the only ones supported by AirMail). Both are small and relatively low-powered (about 1/3 amp at 12 volts). The KAM+ is a second-generation controller, with a simple micro-controller and programmable analog filters, and does a good job with all of the basic modes including Pactor. The SCS PTC-II is a third-generation controller with a powerful DSP (digital signal processor) to handle the modem functions plus a 32-bit microprocessor for the digital chores. All the basic modes are supported plus the new Pactor-2 mode. The choice is economic, with the PTC-II offering much faster and more robust connections at a significantly higher cost. There are other controllers that support Pactor also, such as the PK-232 and MFJ-1278, so if you've got one then use it (AirMail will shortly support the PK family, plans for the MFJ are uncertain).

The Computer:

Almost any sort of computer will do the job. The controllers all have a pretty reasonable command set, and at the basic level any sort of "dumb terminal" program can be used effectively, so even the simplest computer is capable of handling digital communications. For sending more than the occasional message, however, cutting and pasting messages with a dumb terminal program gets pretty tedious and some sort of specialized terminal program such as Airmail will make things much easier.

There are lots of terminal programs available for DOS, Windows and Mac computers, but most are focused on making the multiplicity of controller modes easier to use, and are not oriented toward any specific application. So the value of a conventional terminal program for the job of sending email via Pactor mailboxes is, in our opinion, of little value over typing commands directly to the controller with a dumb terminal program. Being able to cut and paste message text for incoming and outgoing messages is very handy, so being able to run Windows or having a Mac is a significant advantage.

The key to making software programs easier to use is to focus on doing one application well and not try to do everything. And that is why we wrote AirMail. It is a Windows-95 program with a good set of email-style tools for sending and receiving messages via HF Pactor using the PTC-II or KAM controllers (and soon the PK-232), and that's about all.

Installation Basics

There are three cables required to get a controller hooked up: a data cable to the computer, an audio cable to the radio, and a power cable to a 12-volt supply. The data cable sometimes comes with the controller or can be purchased at the computer store. The PTC-II box has a 9-pin female connector with the same pin-out as the 9-pin male found on most PC's, and the KAM has a 25-pin female connector, so both of those are standard computer-store cables. The PK-232 cable is weird and will probably have to be made up special.

The audio cable will have four wires: transmit audio from the controller to the transceiver, receive audio from the transceiver to the controller, a push-to-talk (actually "ground-to-transmit") connection, and ground. The cable must shielded, with the shield connected to the connector shell at each end. The pin connections are different for each controller and each radio, so generally a cable must be made up specially for each configuration. If the radio has a rear-panel "Accessory" connector then that should be the first choice, otherwise the front-panel microphone connector can be used. An accessory jack provides line-level input and outputs and (on most radios) disables the microphone when the rear-panel "PTT" connection is activated.

If you use the microphone connector, you might find a speaker or audio-out connection on same connector, otherwise a rear-panel speaker or audio-out connector can be used. You do not want to disable the speaker completely, however, as it is very important to be able to listen on a frrequency before transmitting. Also consider the TNC/microphone switch ( and thanks to W2WJY for this hint.

And whatever connection you use, be sure that the transmitter audio is not being over-driven, particularly with Pactor-2 (a PTC-II controller). The audio distortion will dramatically reduce the effectiveness of the signal as well as making you a very bad neighbor on the ham bands. The way to check is with the ALC meter, you want it well into the "green", towards the bottom of the dial. Also be sure that any speech compression is turned off for the same reason. You may be able to adjust the transmit audio with the Mic gain control, sometimes there in an internal adjustment, or you can adjust it at the controller (The PTC-II uses the PKSA and FSKA commands, the KAM has a jumper, and the PK-232 has a rear-panel trim pot).

The PTC-II controller uses an 8-pin DIN connector for its HF audio connections, although all of the interesting signals are on pins 1 to 5 so a 5-pin DIN connector will work just fine. And in fact the German pin layout for an 8-pin connector does not match the geometry of the American pin layout, so if you melted the original connector trying to solder it then a 5-pin connector is the safe replacement. The 5-pin connectors from Radio Shack also don’t melt as easily as the German ones.

The relevant PTC-II pin connections are as follows:

Transmit audio (TxD) from the controller to the transmitter
     Pin2 Ground (audio signal return)
     Pin3 Push-to-Talk (PTT), connect to ground to transmit
     Pin4 Receive audio (RxD) from the receiver to the controller
These signals, or something equivalent, will be present on the transceiver's rear-panel accessory connector or front-panel mike and speaker jacks, so simply match up equivalent signals (and keep a drawing of how you did it!).

The KAM also uses a 8-pin DIN connector for its HF audio connections, with pin connections that are almost, but not quite, the same. Either use the pigtail that comes with the KAM or a USA-style 8-pin connector from Radio Shack, a 5-pin connector will fit but will not include pin 6. The KAM pin connections are as follows:

    Pin 1 Transmit audio (TxD) from the controller to the transmitter
    Pin 2 Ground (audio signal return)
    Pin 3 Push-to-Talk (PTT), connect to ground to transmit
    Pin 6 Receive audio (RxD) from the receiver to the controller
The pin numbering for DIN connectors is goofy, so check the manual carefully for the pin locations. Some DIN connectors are also prone to melting while being soldered, so use a clip-in heatsink (or hemostat) on the other end of the pin while soldering, and work quickly.

The power connector used by the PTC-II, KAM and PK-232 controllers is a 5.5mm x 2.1mm coaxial-pin connector (the only thing they all agreed on), also available from Radio Shack (if the controller did not come with one). The center pin is positive, not negative, and the penalty for wiring it backwards is severe. (Note that the PTC-II has an alternate 12V input on its HF audio connector but no corresponding ground return, so we would recommend using the separate power connection for RFI reasons).

A few comments on RFI: A transmitter pumping out 100 watts in digital modes can generate a quite a bit of stray RF, which often finds its way into the controller and computer cables and raises all sort of havoc. The PK-232 seems particularly sensitive to RF, and the PTC-II is pretty immune. A good ground system and shielded cables are a must, and if either of those are deficient then that's a place to start. But beyond that it is usually necessary to add some clip-on ferrites or a coax line isolator to provide RF blocking.

Clip-on ferrite chokes are about 1" long with a 1/4" hole through the middle and act as RF blocks, allowing normal bi-directional signal flow but blocking any common mode (unidirectional) RF current such as stray RF flowing on a ground wire or shield. Their primary function is to break up ground loops and keep the ground currents off of the signal cables where it will couple into everything. Ferrite chokes can be particularly useful clipped onto the audio connection between the PTC-II and the transceiver, ideally one at each end. They are available from Radio Shack, but a better choice is Fair-Rite p/n 0443164251, available from Newark Electronics as their part# 95F763. Another choice is the MFJ-701 from MFJ, an open-frame core which allows multiple turns of cable but which we don't think is as effective as the Fair-Rite choke.

Clip-on ferrites or a ferrite Line Isolator is also highly recommended between the transceiver and the tuner (or between the transceiver and antenna if no tuner is fitted). A line isolator is a much beefier version of a clip-on ferrite choke, and blocks the stray RF path to ground via the coax shield and transceiver ground, forcing the antenna currents to use the proper ground strap. An excellent Line Isolator is model T-4 from The Radio Works, Portsmouth VA (and their web site also has an excellent discussion on grounding and RF interference).

Getting Connected with AirMail

Once things are hooked up and checked, it is time to try out AirMail. (We're also assuming you have a compatable controller and are running Windows-95). AirMail is downloaded as a self-extracting .exe file, so simply double-click the download file from Windows (file) Explorer to install it. AirMail by default installs in the directory Program Files\AirMail and prompts for a path with the default "C:\". The easiest way to install the program elsewhere is to first accept the default and then move the AirMail folder (and sub-folders) and re-do the shortcuts from the start menu and the desktop - the program itself is a self-contained .exe file and is highly portable.

Start the program, answer the callsign question (no /MM here) and before doing anything else go to Tools/Options on the menu and check the settings. On the first page be sure the appropriate controller is selected and the baud rate is correct (we recommend 38400 or 57600 for the PTC-II and 4800 or 9600 for the KAM). Also check "Show Link Messages" for now (and un-check it later after things get going). In the radio section, check "none", "LSB", set the Center Frequency to "2100" and check the "Set Decoder Tones" box. On the next page make sure your callsign is correct and don't worry about the ID string unless you want to identify as a "/mm" for example. Click the OK button (not cancel) to close the Options Window and save the settings.

Now select View/Frequency List from the menu, that will show the list of all available MBO stations. The check boxes mark the stations that will appear in the Station list, and don't forget to save if you made any changes. If you said "What check marks?" then you need to update the Windows Common Controls Driver (comctl32.dll). There is a Microsoft update for that called com32upd.exe available at or wherever you found the Airmail download. (This update used to be bundled with Internet Explorer, but is now available separately at the suggestion of the Justice Department).

Now open the Terminal Window (F6 or Window/Terminal on the menu or click the right-most "Terminal Window" button). Watch the upper screen - after 2-3 seconds it should show a list of setup commands in red - these are the "Link Messages" that you elected to show in the Options Window. The status bar at the bottom should also show "Init OK", but the message is a bit elusive as the same box gets used for hints. If all that worked then you should be ready to connect.

AirMail can communicate with the MBO station in three different modes: BBS mode ("Handshake" button down) is the default and provides automatic message forwarding both ways, you don't have to do a thing except make the initial connection; Keyboard mode ("Keyboard" button down) allows you to enter commands manuall, read bulletins, etc.; and Unprompted mode (neither button down) is completely manual. There are also buttons that allow you to get or send messages in Keyboard mode, but we strongly recommend that you use BBS mode for transferring messages, as it will save time and allow others more access.

If you are new to WinLink MBO's, there are two things we would suggest: First, start with an MBO that isn't particulary busy. K4CJX runs a geat MBO but is very busy, instead try N8PGR or K7SLI. Secondly, make your first contact in "Keyboard" mode so you will have a chance to read the help files and check for bulletins. Once you are up and running, however, you will want to use BBS mode most of the time.

The next step is to select a station from the Station pull-down list (on Terminal Window's Toolbar), that chooses the station that AirMail will try to connect to. (If you don’t pick one first, AirMail will ask when you try to connect). If you don;t see the station you want on this list, then close the Terminal Window and go back up three paragraphs and put a checkmark next to the stations you want to access.

Once you have selected a station from the Station List then click the Frequency List to the right access a list of frequencies scanned by that MBO station. As you move up and down the list, the dial frequency will be calculated and displayed in the status bar at the lower-right (and if you had a remote control cable connected to the transceiver then the frequency would be set automatically - that's a great feature but one to worry about later). For now you may want to put the dial frequencies for your favorite MBO into the transceiver's memory (and remember that the frequency list at the top of AirMail's Terminal Window shows center frequencies, and the selected dial frequency will be displayed in the bottom status bar).

Check all of the frequencies for the selected MBO, listen carefully and choose a clear frequency on an appropriate band, and then try connecting to the MBO. If you are trying to connect to a busy MBO like K4CJX, then you will likely find him busy on another frequency. In this case either find a less-busy MBO, or wait untill he signs off with a "SK" message. When you are ready to connect click the left-most "Green-light" button or select Control/Connect) from the menu). The controller will call for about a minute before timing out, that is usually plenty if the propagation is good and the station is not busy on another frequency. If the MBO doesn't answer then try another frequency or try some other time - the station may be busy on a another frequency or there may be no propagation.

When you get connected to a WinLink MBO, you will see the welcome message and then a command prompt ending with a "", that means "Go Ahead". In Keyboard mode you will be in a semi-automatic mode where you can type commands manually (into the lower keyboard box) but AirMail will hold each command until it sees the next prompt from WinLink. Each command is followed by the Enter key, and WinLink will take care of turning the link around - there is no need for you to initiate a change-over (and doing so will just confuse everyone).

Enter the H (Help) command into the lower keyboard box, and WinLink will return a list of commands and their use. Also try the I (info) command, and enter LB to get a current list of bulletins. If you want to read any of the listed bulletins, enter R and the bulletin number, i.e. R 1234 to read bulletin number 1234. If all that works then logoff (enter a B for Bye) and WinLink will disconnect. If you got this far, then all of the technical stuff is working, the wires are all hooked right and you got the frequencies figured out correctly. If the controller isn't working correctly, then skip ahead to the Terminal Program section and check it out step-by-step.

If you got this far then try composing a test message. Do this by going back to AirMail's main window (F6 to switch or close the Terminal Window) and click the "New Message" button (or File/New from the menu). For now, close the Address Book by pressing the Esc key and then enter "SP CALLSIGN@MBO" on the first line of the new message, where "CALLSIGN" is your callsign and "MBO" is the callsign of the MBO that you want to connect to. ("SP" means Send Private and is the send-message command). The second line is the subject, and the third line starts the message. Don't worry about adding the "/EX" terminator at the end, AirMail will do that. When you are done composing the message, click the "Post" button (or menu File/Post) - that will save the message and mark it for sending, and return you to the index. Your new message should be in the index with a "mailbox" icon next to it indicating it waiting to be sent.

Now go back to the Terminal Window (F6 again), and this time click the "BBS mode" button (the handshake icon). Reconnect to the MBO as before, and this time AirMail and WinLink will exchange system ID's (the square-bracket codes) and handle the transfer automatically (the keyboard is disabled). Uploads go first in BBS mode, so your message should first be uploaded to the MBO, and then should immediately download again (if you addressed it to yourself). WinLink will disconnect automatically when done. Now go back to the Main Window (F6 again) and check your new message.

Sending a message to an email gateway is just as easy. Messages addressed to "Nexus" are routed to the NetLink internet gate, so start a new message with "SP NEXUS@MBO" on the first line, where MBO in this case is the nearest WinLink station that has a Nexus/NetLink gateway. The email address goes on the second line, and the message subject on the third line. Follow that with the message text and post it as before. If the gateway is not at the same station that you normally connect to, then it will be forwarded automatically but you will be prompted for which MBO you want to send the message to (the "Post-to MBO"). AirMail's "Post-to" MBO is where the message will first be sent, and the "@MBO" is where the message will eventually wind up after being forward.

If that all works then it is time to grab your favorite beverage, sit down with the Help files, and start reading. If none of this works, try it with a Terminal Program and then come back here. If the controller didn’t initialize properly then the baud rate may be wrong, or there may be a setting that is incompatible with AirMail. It may also be necessary to restore the default settings if you have been trying other programs, but in general that should not be necessary more than once (if it is, we would really like to hear about it so we can fix it). If all else fails write us with a careful chronology and we'll try to help.

Using a Terminal Program
The first thing to establish is that the controller is communicating with the computer and that the baud rate is set to what you think it is. Windows HyperTerminal is a good choice, it is found under Programs/Accessories in the Start menu, open the HyperTerm folder and double-click "Hypertrm.exe". You will be prompted for a new connection, give it a name like "PTC-II" or whatever and click OK. On the next window change "Connect using" to "Direct to Com 1" or wherever you have the controller connected and click "OK". The next window is Port Settings, set the baud rate to 38400 or 57600 for a PTC-II (4800 or 9600 for a KAM or PK-232, or whatever the controller is set to), 8 data bits, no parity, 1 stop bit and click "OK". Now go to the File menu and select Save to save the settings, and then exit HyperTerminal and restart it. This time you will see an icon in the HyperTerminal folder for your controller settings, double-click that and you should be ready.

One very important thing about HyperTerminal: if you change the port settings (baud rate, etc.) with the File/Properties menu, you must save the settings, exit the program and re-start it before your changes will take effect. This "feature" drove us crazy before a compassionate friend pointed the problem out.

When you power-on a PTC-II it goes into a "quiet" auto-baud state and you need to hit the "Enter" key to set the baud rate and wake it up, you will then see some start-up text and a "cmd:" prompt. The KAM and PK-232 start right up with the pre-set baud rate so you should see the start-up message and the "cmd:" prompt - if it doesn't then you probably have the wrong baud rate. You won’t be able to set a new baud rate (with the KAM's ABaud command or the PK-232's TBaud command) until you can communicate using the old rate (sort of a Catch-22) so some experimentation might be required. A brand-new KAM will come up in an auto-baud mode, so watch the screen and enter a "*" when prompted.

If you can communicate with the controller using HyperTerminal, then you might be up to a basic working level. Unless you are sure the controller is reset to the default defaults (i.e. it is brand new), give it a hard reset command just to make sure. And be sure that the terminal program is set to 8 data bits and no parity (HyperTerminal like to default to 7 bits/even parity - to change it, select File/Properties from the menu, then click Configure and check the settings, and then restart the program before doing anything else).

One very important thing about the KAM: If you start up a new KAM (or one that you gave a Restore Defaults command), and you have not set 8 bits/no parity, then nothing else will ever work. Trust us on this one. (We think the same is true for the PK-232).

To reset a PTC-II to the factory defaults, use the RESTART command. The controller will reset and go back to its auto-baud routine so hit the Enter key and you should see the start-up text and a "cmd:" prompt. For the KAM, use the RESTORE DEFAULTS command (spelled out). The controller will then start its "Auto-baud" thing, so give it an asterisk (*) when it prompts. The PK-232 requires a RESET command to restore its defaults.

Once you see a cmd: prompt, you should be able to enter controller commands. Commands can be upper or lower case, and usually only the first few letters need to be typed. We will indicate the part of the command that is required with capital letters, and the optional letters with lower case. When you enter the command, however, you can use either case. Each command is followed with the Enter key, and (depending on the command) you will usually get an acknowledgement of some sort and a newcmd: prompt.

The next task is to figure out the offset between the advertised frequency of the WinLink MBO stations and your radio dial. We're recommending that you use the radio's lower-sideband (LSB) mode and set the controller's audio tones to a mark and space frequency of 2000 and 2200 respectively, that's an audio center frequency of 2100 Hz. (The PK-232 is fixed at a center frequency of 2210 Hz). In SSB mode the transceiver's dial always reads out the carrier frequency, not the actual transmitted frequency. The difference is the audio frequency, so for tones of 2000/2200 and LSB mode, the transceiver dial must be set 2.1 KHz above the center frequency of the other station. For most MBO's this works out to be an even kilohertz. For example K4CJX (a popular WinLink MBO in the U.S.) operates on an advertised center frequency of 14071.9 (among many others), so you would set your dial to 14074.00. Simple, no? Of course there are lots of other possible tone and offset combinations, and you can also operate USB or RTTY modes (the latter in Pactor-1 mode only), and once you figure out what you are doing there might be good reasons for doing so. But for now, that's an unpaved road.

At this point we are going to split out the PTC-II users for a few paragraphs while we talk about the commands appropriate for that controller, so KAM users should skip down a a couple of paragraphs.

If you have a PTC-II, there are a few commands that you probably want to change from the default settings: Enter the command REMote 0 to turn off remote-control access, CWid 0 to turn off the CW (Morse) auto-ID (which is not required in most countries), and CHOBell 0 to turn off the change-over beeper (it will make you crazy). The way to set the tones to 2000/2200 is by entering the commands TOnes 2, MARk 2000, and SPAce 2200. You will also need to enter your callsign with the Mycall command.

The PTC-II is already in Pactor Standby mode when it powers on, so you are ready to tune around the band and listen for signals (14065-14080 kHz is prime Pactor real estate). To call another station, set the frequency and enter the command C N8PGR (for example). If the other station responds you will see a "link" message from the controller and then a welcome message and a prompt like "KE6RK de N8PGR>" and the link will turn around so that you become the sending station.. Proceed as outlined below "Communicating with WinLink".

For the KAM, the first thing we need to do after a hard reset is get the unit out of the "New User" mode. We may be, but it won’t let us set the tones so it's got to go. Enter the command INtface Term, then set the tones with the commands SHift Modem, then SPace 3000, MARk 2000, SPace 2200. (With the KAM the space tone must always be higher than Mark, even when being set, so setting Space first to a silly-high tone avoids a possible error message). To get into Pactor Standby mode, enter the command PACTOr (with no argument). You can monitor traffic on the air, get the frequency offsets figured out, etc. To get back to the KAM's cmd: prompt, type <ctrl-C> X(i.e. control and "C" keys together, then the "X" key alone). With the KAM, before calling another station, you first need to return to the cmd: prompt by doing a <ctrl-C> X. Next, find a WinLink MBO frequency, type <ctrl-C X to get a cmd: prompt, then enter the command PACTOR N8PGR (for example) to call the MBO station. If you connect, you will see a welcome message and then a prompt like "KE6RK de N8PGR>" and the link will turn around so that you become the sending station.

Communicating with WinLink: The best place to start is by typing the H command (plus Enter after each command), and WinLink will send back a command list. (Also in AirMail's directory as WinLink.txt if you want to study ahead). WinLink handles all changeovers, you don't need to do anything except type commands and text. LB lists bulletins on file, another handy command. To send a message, for example to your own email address, type SP NEXUS, wait for the prompt for "email address:", type your email address, wait for the prompt for "Subj/Msg:" then type a message subject followed by the text of your short test message. End the message with /EX on a separate line. When you are finished or bored type B (Bye) to quit. (Note that these are all WinLink commands - if you want to send a command to a PTC-II controller, hit the Esc key first to get a cmd: prompt (<ctrl-C> for a KAM). But once linked to WinLink, you don’t want to be sending commands to the controller).

If you need to initiate a disconnect (something WinLink normally takes care of when you enter the Bye command), for a PTC-II enter a <ctrl D> (or type Esc to get a cmd: prompt, then DD to force a disconnect). For a KAM, enter <ctrl-C> X to get a command prompt and then A <Enter> to abort the link.

If all that works then your controller is wired right and your transceiver is working. If there are troubles then there's a couple of things to check: If the transmit power level is too high (ALC off the scale) or too low then the transmit audio level needs adjusting. The PTC-II transmit level is adjusted with the FSKA and PSKA commands and KAM has a jumper (it's OK to check the manual on this). Also, stray RF sometimes gets into the computer serial cable or the audio cable to the transceiver. Adding one or more clip-on ferrites helps a lot as we outlined above.


Amtor Amateur Teletype Over Radio, the first popular digital communication protocol which included direct linking between two stations with data acknowledgement and error checking. It is the same mode as commercial Sitor, and has largely been replaced by Pactor on the ham bands. 
APLink An acronym for Amtor/Packet Link, a DOS-based mailbox program by Vic Poor W5SMM and the predecessor to WinLink.
AX.25 A version of the X.25 protocol adapted by hams for VHF Packet radio, which allows multiple stations to share the same radio frequency. Data is broken up into blocks, or packets, which are transmitted and acknowledged independently. AX.25 packet is sometimes used at 300 baud on the HF bands but not with any particular success. 
Clover A higher-speed HF protocol developed by HAL communications, utilizing multiple-tone phase-shift encoding. Effective throughputs are similar to Pactor-II, and it will be long debated which is the better protocol although Pactor-II has clearly won the popularity contest.
DMB (See MBO) Digital Mailbox - An HF mailbox station for storing and forwarding messages, generally running WinLink software. 
DSP Digital Signal Processor, a specialized microprocessor for processing analog signals. Signals are converted to digital form and processed using various mathematical transformations before being converted back to analog form if required for output. 
FSK Frequency Shift Keying. A simple method of sending digital information over radio, where a binary "1" is assigned one tone and a "0" a second tone. These tones are called "Mark" and "Space" after RTTY practice, and are typically separated by 200 hertz on the HF ham bands. 
KAM A popular multi-mode controller manufactured by Kantronics. The current model is the KAM-plus (KAM+), and an enhancement board can be added to older KAM's to make them KAM-E's with the same functionality. The KAM includes all the basic digital modes plus Pactor and G-TOR, a proprietary 300-baud protocol that was never adopted as a standard by the MBO operators.
MBO Mailbox station - same as DMB - An HF mailbox station for storing and forwarding messages, generally running WinLink software.
NetLink A program written by Jim Jennings W5EUT that provides a gateway between a WinLink MBO and Internet email. 
Packet (See AX.25) The protocol used by digital VHF/UHF stations. A few HF stations operate Packet at 300 baud, but it is not considered reliable (at least by Pactor enthusiasts) and is not supported by WinLink.
 Pactor Pactor A digital radio protocol developed by a group of German hams in the early 80's, allowing faster and more reliable communications than Amtor. The name comes from Latin for the "Mediator". Pactor operates at 100 or 200 baud depending on conditions, with net throughput of up to 18 characters per second.
Pactor-II An improved version of the original Pactor protocol, also designed by SCS, the same group that did the original Pactor protocol. Pactor-II is a two-tone phase-shift system rather than FSK, and operates at basic rates from 100-800 baud depending on conditions. Net throughput is up to 140 characters per second depending on conditions.
PSK Phase-shift keying, the encoding method used by Pactor-II and Clover. Multiple frequencies (tones) can be used to transmit more information, and the phase of each tone is shifted to encode a binary "1" or "0".
PTC-II The Pactor-II controller from SCS, a powerful DSP-based controller that also supports all of the basic digital modes (including gray-scale weather fax).
RTTY Radio Teletype. Originally designed for electro-mechanical teleprinters, RTTY generally uses a 5-bit Baudot code and operates around 45 baud. There is no acknowledgement (except from the operator at the other end) and no error checking.
WinLink A Windows program for MBO's which allows simultaneous operation on VHF packet and HF Amtor, Pactor and Clover (with suitable controllers), and provides store-and-forward message handling. WinLink was originally written by Vic Poor W5SMM as a development of his APLink (Amtor/Packet Link) program, and has been extensively rewritten and developed by Hans Kessler N8PGR. 

Digital Modes Samples

Click on a digital mode below to hear a brief (most <100 kilobytes) sample of the sound these modes make. Hopefully this page will help you identify a mode you've heard (or help me identify ones I've heard!).  Many folks have submitted excellent quality, lengthy files which are no trouble for me to accept, but I do generally drop the sampling rate and length to make them more reasonable to download over a dial-up line.  The intent here is more for recognition by ear than for signal analysis.

Sound Acronym Description Common Freqs Links Special Thanks
CW 20 wpm Continuous Wave Continous Wave is technically a modulation scheme, but the term CW is often used interchangeably with Morse Code. This sample is keyed at 20 words per minute. Many repeaters ID in Morse Code.   More info  
RTTY 45 baud Radio TeleTYpe Sends text as 5 bit characters with no error correction. 45 baud is the Amateur standard. 14075 KHz USB More info  
RTTY 75 baud Radio TeleTYpe Same as above, except faster. Commonly used in weather data transfer. 10536 kHz USB    
SITOR-A Simplex Telex Over Radio Sends data in a two frequency mode, one for sending and one for receiving an acknowledge. The brief pause you hear in this sample is where the receiving station sends the acknowledge burst.  Automatic Repeat reQuest guarantees delivery.      
AMTOR ARQ Amateur Teletype Over Radio As above.      
SITOR-B Simplex Telex Over Radio In this case using Forward Error Correction mode, minimizing errors. Identical format used in SITOR - SImplex Teletype Over Radio, and NAVTEX - NAVigational TEleX. 14070, 6330, 518 kHz, respectively    
AMTOR FEC Amateur Teletype Over Radio As above.      
ROU-FEC 164.5/218.3 bd Roumanian FEC See above for FEC explanation. HF band   Unknown
SWED-ARQ Swedish ARQ As above. HF band    
PSK-31 Phase Shift Keyed Currently, a quite popular amateur mode providing highly readable teletext over great distances on low power on narrow bandwidth. HF band    
MFSK Multi-Frequency Shift Keying Sequential multi-tone data mode near 64bps. HF band More info Van Lanphear
VFT Voice Frequency Telegraphy An older USAF RTTY-like data mode HF band    
Hyperfix   A military data or sounding mode. HF band    
Hyperfix   As above. HF band    
ALE Automatic Link Establishment Propagation sounding and messaging used by the military. HF band More info  
SSTV Slow Scan TeleVision Amateur video mode carries images one scan line at a time by using a frequency shift for each pixel. 14230 kHz USB More info Pic from Mir on 145.985
WeFax Weather Fax Used to send weather maps and photos primarily to ships at sea and operates similarly to SSTV 8080 kHz USB    
Packet 300 baud   Amateur Packet radio sends data in bursts at 300 baud, and waits for an acknowledge packet from the other end before sending the next packet. 14105 kHz USB More info  
Packet 1200 baud   As above, but faster. 144.39 NFM, 145.030 NFM    
Bell 103 modem 300 baud   Used by WB9AGH weather wire in a Chicago suburb for transmission of weather info.  Can be decoded with a telephone modem. 147.060 NFM   Scott, Jerry in IL
Pactor   A sort of combination of Packet and AMTOR used by ships and Amateur Radio on HF. HF band    
5/6 tone paging   Used for simple tone or voice pagers or ANI.  This sample has 2 sequences reading 0-123456 when decoded, the first set use an optional preamble.     Steve Donnell
Golay Named after a mathematician Golay is a 600 baud paging signal developed by Motorola. Also, Motorola DPL uses the same protocol format as a subaudible tone set of a 23 bit repeated word sent at a 134.5 Hz rate.     Gary Gray
POCSAG 512 baud Post Office Code Standarisation Advisory Group A paging format originating in the UK, used widely in the US. 152, 454, 929, and 931 MHz US    
POCSAG 1200 baud   As above, only faster.      
POCSAG 2400 baud   As above, faster yet.      
FLEX   Another paging format common in the US.  2 or 4 level signalling as 1600, 3200, or 6400bd rates. 929 and 931 MHz US More info  
ERMES European Radio MEssage System 6250 baud paging format used in Europe 169MHz in France, Hungary, Malaysia More info  
AFSK Paging Link Audio Frequency Shift Keyed At the paging Tx site, this AFSK is decoded into the "digital" FSK format (e.g, POCSAG). 72-75 MHz US, also old mobile phone freqs   Steve D.
FLEX Paging Link?   Pretty sure this is a paging link from terminal to transmitter 940MHz US   EJ Caylor
Speedcall DTMF Dual Tone Multi Frequency Yep, just like telephone dial, but quite rapid.  This particular use is for water utility telemetry.  Also used for other signalling and over the air device activation. About anywhere, as DTMF falls in the passband of most transceivers   anonymous in CA
MODAT   Used as ANI or status indicator, precedes or follows voice.     Lindsay Blanton
GE-Star   Used as ANI or status indicator, precedes or follows voice. 155.445 WI State Patrol D1   Lindsay Blanton, Jake Guild
MDC1200   Used as ANI or status indicator, precedes or follows voice. 154.130 Milw FD   Jake Guild
MDC4800   Mobile Data Terminals (MDTs) used in Police squads. 858.2625, 855.7375 in Milwaukee, WI    
MDC4800 (ARDIS )   Slightly different in sound, Ardis, now Motient, is a packet switched data network for two-way data transfer. formerly 854.8375 in Milwaukee    
MDC4800 (ARDIS at 855.8375)   Somewhat different yet in sound. 855.8375 in Milwaukee    
MDC4800?   SAPOL - South Australian Police 868.7625 MHz   Jon in Australia
RD-LAP 9600 baud Radio Data - Link Access Protocol ? As used by a power utility in Wisconsin. Not fully verified, note similarity to 19.2k variety. 938.9375 in WI by WEPCo    
RD-LAP 19200 baud Radio Data - Link Access Protocol ? Mobile Data Terminals (MDTs) used in Police squads. 856.7375, 857.2625 in Milwaukee, also ARDIS now 854.8375    
DataRadioIP   Mobile Data Terminals (MDTs) used in Police squads. Uses IP as addressing system and allows Voice Over IP 857.2625 Sheboygan Co, WI More info Mike Mannchen
MMP-4800 (MDI)   Mobile Data Terminals (MDTs) used in Police squads and FedEx. Created by a company called Mobile Data International, which was purchased by Motorola.     Charles Guerin, Eric Hoefert
Gandalf Mobile Dispatch   Licensed to American United Cabin Milwaukee area, evidence of MDT usage. 152.42 in Milwaukee, WI   Sean Douglas, anonymous
DDS 4800bd QPSK Digital Dispatch Systems Licensed to Yellow Cab in Milwaukee area, evidence of MDT usage, credit, GPS. 152.33 in Milwaukee, but any NFM poss More info Bob Brown
IP MobileNet   19.2kbps MDT system. TDMA voice capable using INVADR (formerly Electrocom) ( likely 4-level FSK with FEC, native IP communications) 139.375 by the WI State Patrol, 852.6125 Rock Co, WI? More Info Barry W, Jim Korth
ATCS Spec200 Automatic Train Control System 4800 baud data system somewhat similar to MDC4800. US Nationwide license to American Ass'n of Railroads (AAR) Standard 6 base and 6 mobile freqs allocated nationwide US in 935-940 band. More info Dave Huoy
EOTD End of Train Device Used to monitor and control air pressure, etc on US trains.  AAR standard 1200bd FSK protocol. 457.9375, 452.9375 More info 1200/1800Hz Mark/Space
ARES Railroad Telemetry   Used by the BNSF railroad. Data transmission protocol is same as ACARS, datagrams same as ATCS. 161.325, 160.365 Northern IL More info Dave Huoy
Harmon MCS-1/2 base   As used on the CP railroad in WI on the 952MHz band, base side for signal and track control 952.28125 in Jefferson Co, WI   Erik Coleman
Harmon MCS-1/2 wayside   As used on the CP railroad in WI on the 928MHz band, wayside for signal and track indication 928.28125 in Jefferson Co, WI   Erik Coleman
Mobile Data Systems MDS9710 - RR Base   As used on the CN railroad on the ex-IC Dubuque Sub on the 941MHz band, base side  for signal and track control 932.34375 at Freeport, IL    
Mobile Data Systems MDS9710 - RR Wayside   As used on the CN railroad on the ex-IC Dubuque Sub on the 932MHz band, base side  for signal and track control 941.34375 at Freeport, IL    
Union Switch & Signal 550 Flexicode base   As used on the UP railroad on the 952MHz band, wayside for signal and track control 952.13125 on the UP at Ellis, IL   Doug Nipper (sample) Anonymous (ID)
Union Switch & Signal 550 Flexicode wayside   As used on the UP railroad on the 928MHz band, wayside for signal and track indication 928.13125 on the UP at Ellis, IL   Doug Nipper (sample) Anonymous (ID)
Harmon HP-1 Railroad Codeline Base   As used on the CN/IC railroad on the 952MHz band, wayside for signal and track control 952.18125 on CN/IC at Tolono, IL   Doug Nipper
Harmon HP-1 Railroad Codeline Wayside   As used on the CN/IC railroad on the 928MHz band, wayside for signal and track control 928.18125 on CN/IC at Tolono, IL   Doug Nipper
Meteor HLCS Railroad data HyRail Limits Compliance System As used on the BNSF railroad nearly system-wide for vehicle location reporting, detectors, and other statuses. 44.58 (recording from USB and compressed) KC9DRX
Mobitex   As used in US by RAM mobile data. 935-940 MHz band US   anonymous from UK
CDPD Cellular Digital Packet Data Typically uses vacant cellular voice channels to transmit 19200 baud data. FedEx apparently uses a dedicated frequency system in Chicago on 860.8625 and other freqs.     Steve Donnell
Paknet   This is another British commercial data system. It uses an X.25 access system. 164 MHz UK   anonymous from UK
NMT-450 Nordic Mobile Telephones control channel It is a very primitive network (first generation) and uses analog FM with 25 KHz spacing. Similar is NMT-900. 463-470 in Sweden   Alex Skafidas, John Kristian Snekvik, anonymous
LoJack   Not sure what protocol this is, but it is used to direction find stolen vehicles and/or disable ignition. 173.075 nationwide US    
Cognito   This is another British commercial data system 178 MHz UK   anonymous from UK
GSM digital cellular Global System for Mobile This form of digital voice transmission is very common in North America, Europe, and the Middle East 890-915 MHz EU? More info  
D-AMPS Cellular voice Digital-Advanced Mobile Phone Service The TDMA based digital standard for the legacy 800MHz cellular system in the US, allowing for 3 conversations per 30kHz channel. 879-881 MHz US    
AMPS Cellular Control Channel Advanced Mobile Phone Service This channel tells cell phones what channel to use for voice, and other information. 879-881 MHz US More info  
Motorola Type 1 (old) Trunking Control Channel   This 3600 baud channel is used to tell mobile radios which voice frequency to use. 851-869 MHz band US, others More info  
Motorola Type 1 (newer) or  Type 2 Trunking Control Channel   As above, but the sound here is nearly the same for newer Type 1, and all flavors of Type 2, except networked systems. 851-869 MHz band US, others More info  
Motorola Networked Trunking Control Channel   As above, Networked, or "Smartzone" systems use Type 2 style IDs, which can span across many distinct transmitter sites over a wide area. 851-869 MHz band US, others More info  
Motorola ASTRO APCO-25 Trunking Control Channel   This 9600 baud channel is used to tell mobile radios which voice frequency to use. ASTRO is a digital/analog voice trunked radio system.  APCO-25 makes it industry standards compliant for smooth interaction with neighboring systems. 851-869 MHz band US, others More info  
Motorola IMBE (ASTRO APCO-25 Trunked) Digital Voice Improved Multi-Band Excitation This is to be the Common Air Interface (CAI) specified by the APCO-25 standard.  State of MI State Police, also on a 400 MHz military TRS.  The military system is not using a 9600bd control channel, but seems to be using the same voice format.   More info  
EDACS (Ericsson) Trunking Control Channel   This 9600 baud channel is used to tell mobile radios which voice frequency to use. 851-869 MHz band US, others More info  
EDACS (Ericsson) Narrowband Trunking Control Channel   This 4800 baud channel is used to tell mobile radios which voice frequency to use. NIPSCO, the northern Indiana power utility has a multi-site networked system. 935-940 MHz band US More info  
Aegis Digital Voice (Ericsson)   Digital voice format incorporated into EDACS trunked systems.   More info Charles Guerin
VSLEP Digital Voice   Digital voice format as used by Motorola radios prior to IMBE format.   Rich Carlson
OTAR Over The Air Re-key Transmitted to DES capable radios to update encryption key. 160MHz Fed Band US Lindsay Blanton
DES Encryption Digital Encryption System? Probably the most common encrypted digital voice format. Commonly heard on same freqs as analog voice. 160MHz Fed Band US, various PDs  
DES Encryption - Trunked   Same as DES, but on a Motorola trunked system. Note lack of high pitch at end of transmission Motorola TRS  
KY57/58 Encryption   Military Voice encryption standard, heard on aircraft/base comms here UHF air band 376.1 AM Mike Hein, others
Racal Cougar Voice Encryption   Voice Encryption used by military and special law enforement units. Mostly UK. Bob
Voice Inversion Scrambling   Simple voice inversion scrambling.  Not digital, per se, but interesting.   F1 Scanner Group Bob
TETRA Trans-European Trunked RAdio Digital trunked radio, primarily European 390.2375 NFM in Spain   Miquel in Spain, Rickey Stein, and anonymous
EFJ LTR Trunking Control subaudible Logic Trunked Radio EF Johnson trunking format. This subaudible tone sequence is used to tell mobile radios which voice frequency to use. You will need a set of HEADPHONES or speakers/amplifier with plenty of bass response to hear anything as these tones are "SUBAUDIBLE". The audible tones you hear is just a telephone ring. 851-869 MHz band US, others   Bruce in Colorado
M/A-Com - OpenSky Data Network See CDPD, above Apparently uses private CDPD for data.  Voice is a 2 slot TDMA AMBE CODEC from DVSI and likely sounds different from this. 851-869 MHz band Pennsylvania state system More info
220 MHz SEA LTR Trunking Control pilot tone Logic Trunked Radio As heard in NFM, but actually uses ACSB (similar to SSB) for voice comms. The pilot tone is transmitted about every 10 seconds.  In Milwaukee, 220.0125 is one frequency, but you may have to tune up or down a bit to hear it.  Sorry for the scratchy copy, I'll work on a better sample. 220-222 MHz ACSB    
GE MARC-V Trunking   A trunking system which does not use a control channel.  No longer implemented in the US, some systems linger.   More info Isidoro Hernandez, Carolina, Puerto Rico.   Also Matthew Sadler.
Midland CMS Trunking Control   In Jasper, IN area, also in Ottawa, Ont.  David confirmed the type. 857.0875Mhz in Jasper, IN   Chris in IN, David Harris in Ont
MPT 1327 Trunking Control Channel Ministry of Post and Telecom This format is very common in European countries, Australia, and South Africa.  Might be commonly referred to as TaitNet. This channel is used to tell mobile radios which voice frequency to use. More info More info anonymous from UK
MPT1317   A data format found in the UK. It is a variant of MPT1327. 86.5875 MHz UK   anonymous from UK
Motorola iDen (Nextel)   A digital modulation scheme used by the Nextel digital cellular system. 851-869 MHz band US More info  
ACARS Aircraft Communications And Reporting System Used to transmit aircraft waypoint, temperature, performance, and other data between to and from the ground station. 131.55 MHz AM More info  
SCADA telemetry Supervisory Control And Data Acquisition Technically this isn't a mode, but a generic term for a data acquistion means. Some of possible data protocols are SC-1801, Harris 5000/6000/XA-21, Telegyr 8979, TRW-9550, and PERT 26/31. This particular signal is heard in the Milwaukee, Wisconsin area. It is a wide signal spanning 952.250 thru 952.750 MHz with this audio being recorded from the center of 952.500 MHz WFM. I have observed directional 900MHz antennas in use at various utility shacks, so I suppose it could be monitoring or control telemetry from these. 952.50625 MHz WEPCo   anonymous local
SSR Secondary Surveillance Radar used to transmit an aircraft's ID number and altitude to ground controllers. It is otherwise known as a transponder and the transmissions are referred to as "squawks". Aircraft squawk on 1090 MHz when interrogated by ground radar. Listen in SSB or AM mode. 1030, 1090 MHz    
DMB Data Marker Buoy US Coast Guard drops these beacons to pinpoint Search And Rescue positions and monitor drift of wreckage.  Continuous tones. This one was set to 242.65 MHz. I'm told ELT's on 121.5 sound the same. 243, 121.5 MHz AM    
EAS Emergency Alert System tone sequence which has replaced the old EBS annoying tone. These new tones will be used on commercial and National Weather Service radio stations and carry location-specific emergency messages (SAME). 162.4-162.55 MHz FM, bcast radio    
CompuLert FSK-FM Frequency Shift Keying Low speed FSK telemetry to monitor and sound warning sirens.  Milw. Co. Emergency Management uses it for tornado siren telemetry.  Voice is also on this freq. 453.375 Milwaukee, WI More info  
Zetron Model 6/26   1200 baud FSK telemetry for fire station alerting. 154.175 Waukesha, WI More info Frank Monaco
Radionics Safecom   Alarm system telemetry. ? Jon in Australia
GPS RTK Global Positioning Satellite Real-Time Kinematics Not sure if this is a standard protocol, but the signal is definitely being transmitted from a GPS survey unit to improve accuracy, as close as 1 cm various More Info

    Link    Ham_Radio


What does QRP Mean?

  • QRP is transmitting on the Amateur Radio Bands using low power
  • Usually QRP power is 5 watts or less when using CW or other digital modes, while 10 watts or less is generally considered QRP when operating on SSB
  • There is a great sense of accomplishment when you make contacts, sometimes using very simple transmitters or transceivers, at QRP power levels
  • QRP can be used with virtually any mode.  The new digital modes implemented through use of computer sound cards work very well using QRP power levels
    • QRPp usually refers to low power operation when the power of the transmitter is below 1 watt.  
Here's an example of a QRPp transceiver.  Actually smaller than a pack of cigarettes.  The transceiver is named the "Rock Mite" and is a design by Small Wonder Labs.  The kit (less case, jacks and controls) is about $27 and can be ordered for 20 meters or 40 meters.  The standard power output is 500 milliwatts, however by swapping a few components (final, resistor and choke) you can raise the power output from between  1/2 to 1 watt.

This Rock Mite has been modified with a different final than the stock 2N2222A and will output about 750 milliwatts.  I have worked over 10 states with this transceiver using nothing more than this, a 12 volt battery and a Butternut vertical antenna.  The farthest state being Arizona (from Ohio). It only operates on two frequencies just around the standard QRP calling frequecy of 14.060.  My next project is the 40 meter version.

This page is still under contruction and I will add more of my QRP radio collection to this web site soon.


SSB --1.843
SSB --3.690
SSB --3.690
SSB --7.090
SSB --21.285
SSB -- 28.360
SSB --50.285

Amateur Radio Emergency Service (ARES)

Amateur Radio During and After Disasters

Amateur Radio operators set up and operate organized communication networks locally for governmental and emergency officials, as well as non-commercial communication for private citizens affected by the disaster. Amateur Radio operators are most likely to be active after disasters that damage regular lines of communications due to power outages and destruction of telephone, cellular and other infrastructure-dependent systems.

Amateur Radio Operators Help Local Officials
Many radio amateurs are active as communications volunteers with local public safety organizations. In addition, in some disasters, radio frequencies are not coordinated among relief officials and Amateur Radio operators step in to coordinate communication when radio towers and other elements in the communications infrastructure are damaged.

Major Amateur Radio Emergency Organizations
Amateur Radio operators have informal and formal groups to coordinate communication during emergencies. At the local level, hams may participate in local emergency organizations, or organize local "traffic nets."At the state level, hams are often involved with state emergency management operations. In addition, hams operate at the national level through the Radio Amateur Civil Emergency Service (RACES), which is coordinated through the Federal Emergency Management Agency, and through the Amateur Radio Emergency Service (ARES), which is coordinated through the American Radio Relay League and its field volunteers. Amateur Radio Is Recognized as a Resource by National Relief Organizations
Many national organizations have formal agreements with the Amateur Radio Emergency Service (ARES) and other Amateur Radio groups including:

Link arrl

Public Service Communications Manual


The Amateur Radio Emergency Service (ARES) consists of licensed amateurs who have voluntarily registered their qualifications and equipment for communications duty in the public service when disaster strikes. Every licensed amateur, regardless of membership in ARRL or any other local or national organization, is eligible for membership in the ARES. The only qualification, other than possession of an Amateur Radio license, is a sincere desire to serve. Because ARES is an amateur service, only amateurs are eligible for membership. The possession of emergency-powered equipment is desirable, but is not a requirement for membership.

ARES Operation During Emergencies and Disasters

Operation in an emergency net is little different from operation in any other net, requires preparation and training. This includes training in handling of written messages--that is, what is generally known as "traffic handling." Handling traffic is covered in detail in the ARRL Operating Manual. This is required reading for all ARES members--in fact, for all amateurs aspiring to participate in disaster communications.

The specifications of an effective communication service depend on the nature of the information which must be communicated. Pre-disaster plans and arrangements for disaster communications include:

  • Identification of clients who will need Amateur Radio communication services.
  • Discussion with these clients to learn the nature of the information which they will need to communicate, and the people they will need to communicate with.
  • Specification, development and testing of pertinent services.
While much amateur-to-amateur communicating in an emergency is of a procedural or tactical nature, the real meat of communicating is formal written traffic for the record. Formal written traffic is important for:
  • A record of what has happened--frequent status review, critique and evaluation. Completeness which minimizes omission of vital information.
  • Conciseness, which when used correctly actually takes less time than passing informal traffic.
  • Easier copy--receiving operators know the sequence of the information, resulting in fewer errors and repeats.
When relays are likely to be involved, standard ARRL message format should be used. The record should show, wherever possible:
  1. A message number for reference purposes.
  2. A precedence indicating the importance of the message.
  3. A station of origin so any reply or handling inquiries can be referred to that station.
  4. A check (count of the number of words in the message text) so receiving stations will know whether any words were missed.
  5. A place of origin, so the recipient will know where the message came from (not necessarily the location of the station of origin).
  6. Filing time, ordinarily optional but of great importance in an emergency message.
  7. Date of origin.
The address should be complete and include a telephone number if known. The text should be short and to the point, and the signature should contain not only the name of the person sending the message but his title or connection also, if any.

Point-to-point services for direct delivery of emergency and priority traffic do not involve relays. Indeed, the full ARRL format is often not needed to record written traffic. Shortened forms should be used to save time and effort. For example, the call sign of the originating station usually identifies the place of origin. Also, the addressee is usually known and close by at the receiving station, so full address and telephone number are often superfluous. In many cases, message blanks can be designed so that only key words, letters or numbers have to be filled in and communicated. In some cases, the message form also serves as a log of the operation. Not a net goes by that you don't hear an ARL Fifty or an ARL Sixty One. Unfortunately, "greetings by Amateur Radio" does not apply well during disaster situations. You may hear an ARL text being used for health and welfare traffic, but rarely during or after the actual disaster. Currently, no ARL text describes the wind speed and barometric pressure of a hurricane, medical terminology in a mass casualty incident or potassium iodide in a nuclear power plant drill. While no one is suggesting that an ARL text be developed for each and every situation, there is no reason why amateurs can't work with the local emergency management organizations and assist them with more efficient communications.

Amateurs are often trained and skilled communicators. The emergency management community recognizes these two key words when talking about the Amateur Radio Service. Amateurs must use their skills to help the agencies provide the information that needs to be passed, while at the same time showing their talents as trained communicators who know how to pass information quickly and efficiently. We are expected to pass the information accurately, even if we do not understand the terminology.

Traffic handlers and ARES members are resourceful individuals. Some have developed other forms or charts for passing information. Some hams involved with the SKYWARN program, for instance, go down a list and fill in the blanks, while others use grid squares to define a region. Regardless of the agency that we are working with, we must use our traffic-handling skills to the utmost advantage. Sure, ARL messages are beneficial when we are passing health and welfare traffic. But are they ready to be implemented in times of need in your community? The traffic handler, working through the local ARES organizations, must develop a working relationship with those organizations who handle health and welfare inquiries. Prior planning and personal contact are the keys to allowing an existing National Traffic System to be put to its best use. If we don't interface with the agencies we serve, the resources of the Amateur Radio Service will go untapped.

Regardless of the format used, the appropriate procedures cannot be picked up solely by reading or studying. There is no substitute for actual practice. Your emergency net should practice regularly--much more often than it operates in a real or simulated emergency. Avoid complacency, the feeling that you will know how to operate when the time comes. You won't, unless you do it frequently, with other operators whose style of operating you get to know.

What is MARS?

The Military Affiliate Radio System (MARS) is a Department of Defense sponsored program, established as separately managed and operated programs by the Army, Navy-Marine Corps and Air Force. MARS members are volunteer licensed amateur radio operators who are interested in providing auxiliary or emergency communications to local, national and international emergency and safety organizations, as an adjunct to normal communications.

The primary concept of MARS is to meet the requirements of training for any communications emergency. To this end, organization, methods and facilities must be adequate to meet any emergency requirements and must be flexible in order to provide for rapid expansion. Normal methods must be such that only minor changes will be required when shifting to an emergency status.


The Mission of the MARS system is to:

  • provide auxiliary communications for military, federal and local disaster management officials during periods of emergency or while conducting drills in emergency procedures.
  • assist in effecting normal communications under emergency conditions.
  • create interest and furnish a means of training members in military communications procedures and provide a potential reserve of trained communications personnel.
  • handle morale and quasi-official message and voice communications traffic for members of the Armed Forces and authorized U.S. Government civilian personnel stationed throughout the world.
  • provide, during daily routine operations, a method of exchanging MARSGRAMS and two-way telephone contacts between service personnel and their families back home. In carrying out this assignment, MARS operates a 24-hour message relay system and maintains a series of electronic mailboxes throughout the world.
  • conduct daily traffic and training nets, drills and critiques to train operators and test the systems readiness to handle demands during an emergency.
           Link       navymars

Image Comunication

Link         hffax

First at all you need a Single Side  Band (SSB) Receiver, tune in to a Fax signal, in the Upper Side Band (USB),  at a frequency 1.9 KHz lower as given in theFrequencies lists.
Example  to tune in Northwood on 11.086.5 KHz set your Receiver to 11.084,6 KHz.

The most Fax transmissions are send with a LPM (RPM) of 120  and a IOC (sometimes called Module) of 576. 
Only stations with Russian equipment sometimes use RPM 60 or 90 and sometimes a IOC of 288.
Photofax transmissions such as from north Korea use RPM 60 and a IOC  352 with gray tones, and satellite rebroadcast use also RPM 120 IOC 576, with gray tones (4 or more bit Depth)

For software decoding best way is to decode with Black and White (2 bit Depth).

The Start-tone is 95 % black and 5 % white with tones with a duration of 15 to 20 seconds (called phasing) (300 Hz), the stopsignal is 450 Hz, and  this is called Automatic Picture Transmission ( APT).

Now you should heard the typical "Scratch" sound from a Fax signal, with white-tones are send with  2300 Hz, and black-tones are send with 1500 Hz.

If you use Software for  decoding Fax transmissions, use B&W with 2 bit Depth for the  B&W weather charts


Receive the RTTY Synop Data via Shortwave and  plot your own Weather Maps with SKYVIEW SYNOP from Skyview Systems UK ( Germany Supra PC SYNOP from SupraTec)


The NAVTEX system is used for the automatic broadcast of localised Maritime Safety Information (MSI) using Radio Telex (also known as Narrow Band Direct Printing, or NBDP).

The system mainly operates in the Medium Frequency radio band just above and below the old 500 kHz Morse Distress frequency. System range is generally 300 or so nautical miles from the transmitter.

The NAVTEX system is designed to be used in GMDSS Sea Area A2, and is utilised mainly by those countries with relatively small areas of coastline and/or sea areas to cover.

Major areas of NAVTEX coverage include the Mediterranean Sea, the North Sea, coastal areas around Japan and areas around the North American continent

Frequency of operation

The NAVTEX system has been allocated three broadcast frequencies:

518 kHz the main NAVTEX channel

490 kHz - used for broadcasts in local languages (ie: non-English)

4209.5 kHz - allocated for NAVTEX broadcasts in tropical areas - not widely used at the moment.

All broadcasts from stations within the same NAVAREA must be coordinated on a time sharing basis to eliminate interference.

In addition, power outputs from each station are adjusted to control the range of each broadcast. This is particularly important during night-time hours, as Medium Frequencies always travel further after dark.



WEFAX stands for Weather Facsimile and is similar to other types of fax transmissions. There are currently three different countries that transmit WEFAX, these are the US (GOES), European (Meteosat) and Japanese (GMS ) satellites.

WEFAX is a way of getting monochrome analogue picture information through a standard voice audio channel.  The signal varies rapidly in 
frequency and is sampled from a few hundred times per second to a few thousand times per second depending on the type of WEFAX transmitted. 
The varying tones correspond to varying shades of gray that the satellite sees as  it scans the earth.

The earth is scanned every half-hour where the raw data is transmitted to a receiver station requiring a 60' dish with sophisticated computing equipment. 
The data is reformatted in real time with political boundaries added and transmitted to the satellite where it is retransmitted back to earth at 1691 MHz. A 1691 MHz down converter and a small dish antenna are required to receive WEFAX.

The WEFAX images received are cut into 800 by 800 pixel sections and annotated. The 800 lines of an image each take 250 ms to transmit; hence a whole picture takes about three and a half minutes to receive. A schedule is published detailing what pictures are transmitted at which times and on what channel


 Meteorological satellite radiometers measure outgoing radiation through broad spectral intervals called atmospheric windows. Radiation passes here without severe attenuation by the intervening atmosphere.

Weather satellites do not have sensors that cover the visual spectrum to produce true colour images. They have multiple image sensors onboard that covers the red portion of the spectrum (visual) to the Infrared (IR).
Visible images are produced by reflected solar radiation that directly illuminates the earth; this is only available for daytime weather watching.

Visible satellite images provide information about the observed cloud cover.
Areas of white indicate clouds while shades of gray indicate clear skies, this is because thicker clouds have  a higher reflectivity and appear brighter on a visible image than thinner clouds

IR imaging is needed, as weather watching is essential day and night. Colour enhanced infrared satellite  images are measurements of temperature thus only the differences in temperatures are visible. In an IR image darker is warmer and lighter is colder. Low clouds tend to be warmer than higher clouds. Most  satellite images on TV are IR.

Water vapor images are useful for pointing out regions of moist and dry air.
This provides information about the swirling troposphere's wind patterns and jet streams. Darker colours  indicate drier air while moisture in the air is seen as white.

Automatic Picture Transmission

Automatic Picture Transmission (APT) is used by Satellites to enable a fully automated unattended reception of the transmitted pictures.
At the start of the transmission a start tone is transmitted for some seconds, which is recognised by the receiving unit. 
At the end of the transmission a stop tone is sent that switches the receiving unit back to standby mode.  
The Meteosat and other Geostationary satellites (GOES/GMS/GOMS) have also Digital High Resolution transmissions, which needs special equipment.

It is also possible to receive data from various Polar Orbiting satellites and this may well be the cheapest option, but it does have limitations.
The hardware for this consists of a VHF antenna (the most popular being a crossed dipole), a receiver (137 MHz band) and a suitable software package for displaying on a PC.
Satellites in Polar Orbit are much closer to the Earth surface (around 800-1000 km) and so the image scanned is of a much higher resolution.
The satellite scans what is directly beneath it so in higher latitudes the curvature of the Earth does not pose a problem of the data being invalid, as is the case with Geostationary data.
The NOAA Polar Orbiters are placed in a sun synchronous orbit which means that they will pass overhead at approximately the same time of day.
Unlike the imagery from Meteosat which lends itself to creating animation’s, Polar Orbiter data cannot be animated easily.
The satellite when it passes may be within view of your antenna for about 12 minutes but it will not be following the exact same path overhead and so each captured image will differ.
In order to receive data from Polar Orbiters your ground station needs to be visible from the satellite so if  you wanted data from other parts of the world you would either have to take your equipment with you to that part of the world or swap data with another station. 
 The Polar Orbiter satellites have also Digital High Resolution transmissions (HRPT), which needs special equipment.

HRPT - High Rate Picture Transmission

The High Rate Picture Transmission (HRPT) service installed on the NOAA satellites has for some two decades been  the main source of high quality data from polar orbiting meteorological satellites at major user stations throughout the world.

 The data stream not only contains full resolution images in digital format from the AVHRR instrument but also the atmospheric information from the suite of sounding instruments.

 Through HRPT reception the user site can acquire data from three or more consecutive overpasses twice each day from each satellite, giving high resolution data coverage of a region extending to about 1500 km radius from the user station. 
The imagery gives a snapshot of the meteorological conditions and can also be used for many land and ocean applications, while the sounding data gives detailed atmospheric data that may be processed and used in regional Numerical Weather Prediction (NWP) models.

The NOAA HRPT system provides data from all NOAA-K,L,M spacecraft instruments at a transmission rate of 665,400 BPS.
The real-time transmissions in S-band (at around 1700 MHz) include the digitised unprocessed output of the following sensors:


What is the APT/WEFAX to LRPT/LRIT transition?

During the next ten years, there will be a transition of the present low-resolution satellite services called APT and WEFAX to Low Rate Picture Transmission (LRPT) and Low Rate Information Transmission (LRIT), respectively. The transition will have a direct and potentially large impact on existing and planned ground receiving equipment belonging to WMO Members. The following is a description of the activities undertaken by the Secretary-General to inform and assist Members during the transition.

In February 1998, the Secretary-General informed WMO Members of an initiative within the Secretariat, which has three phases. First, Members will be notified of the status of the conversion on a regular and as required basis. Secondly, and in order to assess the extent of required changes, Members will be advised of the information held by the WMO Secretariat with regard to receiving equipment in their country. The present level of information is not complete enough to advise them adequately of necessary software and/or hardware changes to enable reception of the new digital services and thus, they will receive a request for additional information. Based on this new information and through Secretariat interactions with the satellite operators (both at meetings of the Coordination Group for Meteorological Satellites, CGMS, and bilaterally) and manufacturers, they will be advised of necessary actions they must undertake to enable reception. Finally, Members will receive a new (to be developed) Technical Document describing how to exploit the new digital services. The updating of information will occur during the first half of 1998 and subsequent notification of necessary actions will occur when available. The new Technical Document should be available prior to the commencement of the new digital service. Extensive use of the WMO Satellite Activities Home Page on Internet will be used to facilitate notification.

Tables were distributed in the February 1998 letter showing the status for LRIT and LRPT conversion for satellites in polar and geostationary orbit. The tables were reviewed at the Twenty-fifth session (June 1997) of the Coordination Group for Meteorological Satellites (CGMS). At CGMS-XXV, the satellite operators discussed the dates when the new digital services would commence for their satellite systems and the duration of a transition period when both analogue and digital services would be available.

An analysis of the table for LRIT conversion indicates that in WMO Regions I (Africa) and VI (Europe) there will be a three-year overlap starting in December 2000. WMO Regions II (Asia) and V (Southwest Pacific) will have a three-year overlap starting in March 2000. WMO Regions III and IV (South, Central and North America including the Caribbean) have not yet identified a transition date. The Indian Ocean area (RA-II) appears to have no overlap starting in 2002. An analysis of the table for LRPT conversion shows that the morning (AM) satellite will start LRPT in 2002 while the afternoon (PM) satellite will start LRPT in 2009. Since there will be no transition period for the AM orbit or PM orbit separately, but rather a seven year period when both APT (PM) and LRPT (AM) will be available, it will be necessary to maintain a dual capability (APT and LRPT) during the period 2002-2009 if it is deemed necessary to have information from AM and PM satellites. It can also be seen that the inclusive transition period for all Regions will cover the period from 2000 until 2009 or more.

 Wx Satellite


Receiving Wefax photos on  Short-wave

The reception of meteorological satellites has become a  more child’s play last years. Due to digital hard and software technology puts real-time satellite images on your PC monitor.
Inexpensive  software such as WXSat or JVComm connect to a Wefax receiver  allows you to decode Geostationary and Polar Orbiter Satellites.
For  more then 10 years it was very expensive to receive "live" such images, but for Mariners, Meteorologists, Pilots and Yachtmens, the consultation  of Satellite pictures was a daily routine. These users used the Long and  Short-wave transmissions to receive Satellite pictures.
Due to propagation and fading signals on the short-wave bands they use Frequency  Modulated (FM) transmissions instead of Amplitude Modulation (AM) transmissions from the Satellites.
The drum speed in use on short-wave  is 120 (lines scanned per minute) and the index of co-operation (IOC) in  use is 576. A standard document with a length of 495 mm and a drum  diameter of 152 mm needs 18,8 minutes.
In the past you could receive  daily hundreds of Satellite "retransmission’s" world-wide, but due to modern satellite technologies more and more stations ending the services  on short and long wave to change to the new satellite technologies.
Due  to the propagation on the short-wave bands it is possible to receive all  stations from any location worldwide.
At the moment we go to the maximum of the "11 year solar cycle" which means you have excellent  signals over very long distances.
Radio fax stations transmitting most of the time weather charts who are the best way to interpret the satellite images such as forecasts and tracking of hhurrican/typhoon  weatherforcasting in this area.
At the moment there are 7 Radio fax  stations around the globe who transmit daily on the short-wave bands  Satellite "retransmission’s" from the stations area.

Satellite tracking system for radio amteur and observing puposes It's also used by weather professionals, satellite communication users, astronomers, UFO hobbyist and even astrologers. Application shows the  positions of satellites at any given moment (in real or simulated time). It's FREE (Cardware) and it's probably one of the easiest and most powerful satellite trackers, according to opinions of thousands of users from all over the world. 


  • NORAD SGP4/SDP4 prediction models
  • 20 000 satellites can be loaded from TLE file(s) (auto: PC/Unix, 2/3 line)
  • ALL of them can be tracked at the same time
  • Sun and Moon tracking
  • full screen, presentation modes
  • supported screen resolutions from 640x480
  • Real-time mode / Simulation mode (free time control)
  • advanced passes & Iridium flares search engine (results printing)
  • miscellaneous options of visualisation
  • nightlife (dark color scheme for night usage)
  • orbit info
  • notes for each object
  • radar
  • easy, flexible interface
  • database of cities around the world
  • database of satellite frequiencies
  • PC clock synchronization via NTP
  • Internet TLE updater (with ZIP support) via HTTP
  • rotor/radio control (built-in or user's driver support)
  • Windows screen saver included
  • translations supported


Dartcom GVAR Ingester software

GOES variable format image acquisition, display and processing system

The Dartcom GVAR system is a high-performance, high-reliability solution for ingesting GVAR data from GOES satellites in real-time. It provides full display and processing facilities for the resulting infra-red, visible and water vapour images.

Key features of the Dartcom GVAR system are:

  • Supports GVAR data from GOES 8, 9, 10, 11, 12 and 13 with automatic detection during ingest.
  • Optional GOES LRIT module and software.
  • High-resolution digital data (0.8km visible, 4km infra-red) with calibrated temperature read-outs from infra-red images.
  • Easy installation, with the antenna mounted on a single post and one cable feed to the receiver.
  • Direct read-out of the GVAR data stream for interference-free images.
  • Data transferred from the receiver to the computer via a 12Mbit/s USB connection to ensure high speed and data integrity.
  • High-quality, high-reliability equipment for trouble-free, long-term, continuous operation.
  • Fully automatic Windows-based Dartcom GVAR Ingester data ingest software.
  • Dartcom MacroPro automatic processing software to automatically enhance, mask, print, animate, reproject and create products from ingested GVAR data.
  • Dartcom iDAP display and processing software offering facilities such as image enhancement, product creation, projection transformation, land and sea masking, printing and exporting.
  • Ideal for aviation weather information systems, storm warning systems, forecasting, agriculture, oceanographic studies, and environmental and meteorological programmes.


Acquisition, processing and display systems for LRIT and HRIT data from EUMETCast, MSG, GOES and MTSAT

The Dartcom LRIT/HRIT systems receive, archive, display and process digital LRIT and HRIT data from EUMETCast*, MSG direct broadcast*, GOES and MTSAT. LRIT and HRIT data is an important source of information for nowcasting, numerical weather prediction, climate monitoring and research. The latest MSG HRIT imagery is available every 15 minutes – twice the frequency of the previous generation WEFAX and HRI systems. Coupled with the high quality and wide range of data available, this allows major improvements in the forecasting of severe weather.

Multi-plane HRIT image of northern Africa

The types of data available include:

  • High-resolution digital images with up to 12 spectral bands and up to 1km spatial resolution.
  • Products such as atmospheric motion vectors, cloud analysis, cloud height, global instability index, total ozone and tropospheric humidity.
  • MDD, DCP, DCS, EMWIN and GTS messages.
  • Rebroadcast foreign satellite images.

Dartcom offers systems for EUMETCast (Ku-band and C-band) and MSG direct broadcast, GOES and MTSAT (L-band) comprising:

  • Dish antenna and LNB/downconverter.
  • DVB receiver for EUMETCast, or USB LRIT receiver or combined LRIT/HRIT receiver rack for MSG direct broadcast, GOES and MTSAT.
  • Dartcom XRIT Ingester software to automatically acquire, decrypt, decompress, archive and output LRIT and HRIT data in real time.
  • Dartcom MacroPro automatic processing software to automatically enhance, mask, print, animate, reproject and create products from ingested LRIT and HRIT data.
  • Dartcom iDAP display and processing software offering facilities such as image enhancement, product creation, projection transformation, land and sea masking, printing and exporting.

For a complete turnkey solution Dartcom can also supply the computer hardware and provide installation services and training courses.


Meteorological information through touch-screen interactive display system

The Dartcom MITTS system provides a quick, accessible, easy-to-use way of viewing images and animations using a simple, touch-screen interface. By linking to Dartcom image capture systems for the types of data required, MITTS lets users view and explore the latest weather satellite images and animations from all parts of the globe, including Europe, the USA and the Far East.

MITTS is client-configurable, allowing up to twelve different images and animations to be specified. All fonts, colours, pictures, icons and text can be changed according to requirements, even whilst the system is on-line. Images and animations are automatically updated as new data is received by the optional image capture systems.

MITTS is ideal for use in museums, tourist centres, travel agencies, operational meteorological briefing stations and airports, for example.

Image viewing screen

Features of the Dartcom MITTS system include:

  • Intuitive user interface with large, clear icons.
  • On-line help available instantly at all times.
  • Panning, scrolling, magnification, reduction and printing (if specified) of images.
  • Automatic updating of images and animations with the latest data, even whilst on-screen.
  • Custom images and animations can be specified according to customer requirements.
  • All visual aspects client-configurable.
  • Ideally suited to multi-terminal network use.
  • Remote configuration of MITTS terminals from any computer on the network.



catalao carlos,
21/09/2009, 12:20