moduri digitale
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D-STAR (Digital Smart Technologies for amator radio ) tehnologie introdusa de ICOM
Voice is encoded as a 3600 bit/s data stream using proprietary AMBE encoding, with 1200 bit/s FEC, leaving 1200 bit/s for data encoding. On air bit rates are 4800 bit/s over the 2 m, 70 cm and 23 cm bands.
Digital only data can be sent at 128 kbit/s only on the 23 cm band. Radios providing data service use a RS-232 or USB connection for low speed data (1200 bit/s) and Ethernet for high speed (128 kbit/s) connections to allow easy interfacing with computer equipment
Icom D-STAR >> echipamente
Icom ID-1 - 23cm Digital Voice and Digital Data mobile transceiver. Power is selectable at 1W or 10W. USB Control port and Ethernet connection for data.
Icom IC-2200H
2m single band Digital Voice mobile transceiver. Power up to 65W. Must purchase optional D-STAR module. manual.pdf
Icom IC-V82
2m single band Digital Voice transceiver. Power up to 7W. Must purchase optional D-STAR module.
Icom IC-U82
70cm single band Digital Voice transceiver. Power up to 5W. Must purchase optional D-STAR module. manual.pdf
Repeater Equipment:
- Icom ID-RP2000V - 2m Digital Voice repeater. manual.pdf
- Icom ID-RP4000V - 70cm Digital Voice repeater. manual.pdf
- Icom ID-RP2V - 23cm Digital Voice repeater. manual.pdf
- Icom ID-RP2D - 23cm Digital Data access point.
- Icom ID-RP2C - Repeater controller. Can support up to 4 Digital Voice Repeaters/Digital Data access points. Required to operate any Icom D-STAR Digital Voice repeater or Digital Data access point
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APCO / P25 for public safety
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click pt. video
Utilizing TDMA technology with two alternating time slots within a single 12.5 kHz. In other words, the repeater can handle two separate QSO's simultaneously within the bandwidth of 12.5 kHz. In effect, it's like having two repeaters in one. Talk about spectral efficiency! A repeater must be used in order to take advantage of the two time slots (two virtual channels). The radios also come standard with the capability of text messaging via the keypad or enhanced palm mic. As an added plus, you can verify if the target radio of which you would like to communicate with is on and in range before attempting to call the operator
and or sending it a text message. 
TETRA NEWS 
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TETRA uses a digital modulation scheme known as π/4 DQPSK, this is a form of phase shift keying. The symbol (baud) rate is 18,000 symbols per second, and each symbol maps to 2 bits, thus resulting in 36,000 bits/s gross. As a form of phase shift keying is used to transmit data during each burst, it would seem reasonable to expect the transmit power to be constant. However it is not. This is because the sidebands, which are essentially a repetition of the data in the main carrier's modulation, are filtered off with a sharp filter so that unnecessary spectrum is not used up. This results in an amplitude modulation and is why TETRA requires linear amplifiers. The resulting ratio of peak to mean (rms) power is 3.65 dB. If non-linear (or not-linear enough) amplifiers are used, the sidebands re-appear and cause interference on adjacent channels. Commonly used techniques for achieving the necessary linearity include cartesian loops, and adaptive predistortion.
The base stations normally transmit continuously and (simultaneously) receive continuously from various mobiles - hence they are Frequency Division Duplex. TETRA also uses TDMA (see above). The mobiles normally only transmit on 1 slot/4 and receive on 1 slot/4 so they are both Time Division and Frequency Division Duplex.
Speech signals in TETRA are sampled at 8 kbit/s and then compressed with a vocoder using a technique called ACELP (Adaptive Code Excited Linear Prediction). This creates a data stream of 4.567 kbit/s. This data stream is error-protection encoded before transmission to allow correct decoding even in noisy (erroneous) channels. The data rate after coding is 7.2 kbit/s - the capacity of a single traffic slot when used 17/18 frames.
A single slot consists of 255 usable symbols, the remaining time is used up with synchronisation sequences and turning on/off etc. A single frame consist of 4 slots, and a multiframe (whose duration is 1.02 seconds) consists of 18 frames. Hyperframes also exist, but are mostly used for providing synchronisation to encryption algorithms.
The downlink (i.e. the output of the basestation) is normally a continuous transmission consisting of either specific communications with mobile(s), synchronisation or other general broadcasts. All slots are usually filled with a burst even if idle (continuous mode). Although the system uses 18 frames per second only 17 of these are used for traffic channels, with the 18th frame reserved for signalling, Short Data Service messages (like SMS in GSM) or synchronisation. The frame structure in TETRA (17.65 frames per second = 18 frames in 1.02 seconds), consists of 18000 symbols/s / 255 symbols/slot / 4 slots/frame, and is the cause of the perceived "amplitude modulation" at 17 Hz and is especially apparent in mobiles/portables which only transmit on one slot/4. They use the remaining three slots to switch frequency to receive a burst from the basestation two slots later and then return to their transmit frequency (TDMA).
terminale
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FDMDV Frequency Division Multiplex Digital Voice
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Digital Audio over HF SSB
New Digital Voice Mode
FDMDV is the latest digital voice mode on HF - it caters to high quality digital voice under poor band conditions, in only 1100Hz bandwidth!.
More information about the mode will be posted soon - please check back often for new updates!
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