Shortwave Listening

⏱️ Time & Frequency Standards — A Shortwave Listener’s Toolkit

Many countries operate standards stations to provide precise time and frequency references. In the U.S., the National Institute of Standards and Technology (NIST) runs two such stations:

• WWV – Fort Collins, Colorado

• WWVH – Kauai, Hawaii

Both transmit on 2.5, 5, 10, 15, and 20 MHz, using high-power AM signals that are easy to receive with most HF radios — no sideband capability required.

📌 Why Tune In?

1. Time Announcements

WWV and WWVH announce the time every minute, synchronized to atomic clocks accurate to 2 millionths of a second per day.

2. Instant Propagation Check

By scanning their frequencies, you can quickly assess which parts of the shortwave spectrum are active or “dead” — a handy real-time propagation tool.

3. Solar Forecasts

At 18 minutes past the hour (WWV) and 45 minutes past (WWVH), you’ll hear the Solar Terrestrial Activity Report — a “space weather” forecast that helps guide your listening or operating strategy.

🌐 Bonus: You can also view this data online at solen.info/solar

🔊 Voices & Modes

• WWV uses a male voice

• WWVH uses a female voice

This helps distinguish them when signals overlap.

🌎 Other Standards Stations

• CHU (Canada) – 3.33, 7.85, and 14.67 MHz

• HD2IOA (Ecuador) – 3.81 MHz

• LOL (Argentina) and PPU (Brazil) – occasionally audible on 10 MHz, depending on conditions and WWV signal strength

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🌐 International Broadcast — Voices from Around the World

International broadcasters use high-power AM transmissions that are easy to receive with most shortwave radios. Just tune around randomly and you’ll hear stations from across the globe — some in English, others in their native languages — offering a rich mix of news, music, and cultural programming.

While many national services have shut down due to budget cuts and shrinking audiences, plenty of stations still remain, and they’re a fantastic way to hear perspectives and sounds you won’t find on local airwaves.

📻 Why Listen?

• Global news with unique viewpoints

• Music and culture from distant regions

• Language immersion for curious ears

• DX fun — catch signals from halfway around the world

📡 Popular Shortwave Broadcast Bands

• 3.9 - 4 MHz ("75 meters")

• 4.75 - 5 MHz ("60 meters")

• 5.7 - 6.3 MHz ("49 meters")

• 6.9 - 7.6 MHz ("41 meters")

• 9.2 - 9.9 MHz ("31 meters")

• 11.5 - 12.2 MHz ("25 meters")

• 13.5 - 13.9 MHz ("22 meters")

• 15.0 - 15.8 MHz ("19 meters")

• 17.4 - 17.9 MHz ("16 meters")

• 18.9 - 19.0 MHz ("15 meters")

• 21.4 - 21.9 MHz ("13 meters")

There are also a number of broadcasters who transmit outside these ranges, especially the growing number of Christian evangelical stations.

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✈️ Aviation on Shortwave — Listening to the Skies

While aircraft typically use VHF radios for most communications, they switch to HF (shortwave) when flying far over oceans or remote regions. HF’s long-distance propagation makes it essential for international flight operations.

🗺️ Who’s Talking?

• MWAR (Major World Air Route) stations: Handle routine communications across global air corridors.

• LDOC (Long Distance Operational Control): Used for flight tracking, position reports, and operational updates.

• VOLMET stations: Broadcast continuous weather reports for pilots worldwide — including METARs and TAFs.
  
  

These transmissions are often in USB (Upper Sideband) mode and can be heard with a general coverage HF receiver.

📡 Common Aviation HF Frequency Range

• 2.85 - 3.155 MHz

• 3.40 - 3.5 MHz

• 4.65 - 4.75 MHz

• 5.45 - 5.73 MHz

• 6.525 - 6.765 MHz

• 8.815 - 9.04 MHz

• 11.175 - 11.4 MHz

• 13.2 - 13.36 MHz

• 15.01 - 15.1 MHz

• 17.9 - 18.03 MHz

• 21.85 - 22 MHz

• 23.2 - 23.35 MHz

The most commonly heard in northeastern North America include:

• New York City: 6.604, 8.933 & 10.051 MHz

• North Atlantic: 4.675, 5.598, 5.616, 5.649, 6.628, 8.825, 8.864, 8.891 and 8.906 MHz

• Gander, Newfoundland: 4.677 and 13.27 MHz

• Shannon, Ireland: 5.505 & 8.957 MHz

Aviation communications use sideband mode, so you will need a radio with this feature to listen to these types of signals.

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⚓ Maritime Communications on Shortwave

Like aircraft, ships rely on short-range VHF radios near shore, but switch to long-range HF (shortwave) when venturing far out to sea. These communications typically use sideband mode, and while many transmissions are still accessible to shortwave listeners, a growing number are being converted to encrypted digital formats — making them unintelligible to third parties.

📡 Common Maritime HF Ranges

• 4.35 – 4.44 MHz

• 6.2 – 6.5 MHz
  
  

These bands are used for ship-to-ship and ship-to-shore communications, often in USB (Upper Sideband) mode.

🌊 Maritime Weather & Safety Broadcasts

Dedicated stations also provide vital updates on:

• Wave height

• Storm activity

• Iceberg warnings

• Navigational hazards

These broadcasts are also in sideband mode and can be a fascinating listen for shortwave enthusiasts — especially during active weather events. The most commonly heard in northeastern North America are:

• Boston: 4.235, 6.3405, 9.11 & 12.757 MHz

• Halifax: 4.271, 6.496, 10.536 & 13.51 MHz

• Portsmouth, NH: 4.316, 4.426, 6.314, 8.43 & 8.764 MHz

These stations alternate between voice reports and FAXed maps that can be decoded using inexpensive software (my favorite application for decoding weather FAXes is MultiPSK, which is available free from DXzone.com).

Two frequencies are set aside for distress purposes: 2.182 & 4.125 MHz. Park your radio on one of these from time to time - you never know what you'll hear!

(Note from Gil: The Maritime Mobile Service Net is operational every day from 12:00pm until 9:00pm Eastern Standard Time, and from 12:00pm until 10:00pm Eastern Daylight Time, on the 20-meter Global Emergency Center Of Activity frequency of 14.300 MHz (USB) as specified by the International Radio Union.)

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🪖 Military

Although most military communications today use encrypted digital modes, voice transmissions in the clear (typically in USB sideband) are still active and can be received with the right equipment.

📡 Easiest to Hear in the Eastern U.S.:

CAMSLANT Chesapeake(Communications Area Master Station – Atlantic, Chesapeake, Virginia)

• 5.69 MHz

• 5.696 MHz

• 8.980 MHz

• 8.983 MHz
  
  

U.S. Global High Frequency System

• 6.712 MHz

• 6.739 MHz

• 8.992 MHz

• 11.175 MHz

These signals — like maritime voice transmissions — require a receiver with single-sideband capability.

CB & Amateur
CB operators (mostly truckers) use a portion of the shortwave (HF) "spectrum", from 26.965 to 27.405 MHz, for their communications. Almost all CB users utilize AM mode, so sideband capability is not necessary. The "trucker's channel" frequency is 27.185 MHz -- or Channel 19.

Amateur ("ham") radio operators are major users of shortwave (HF) radio. Most talk using sideband mode, but some still use the original digital mode, morse code since it typically reaches farther than voice. It can be decrypted by numerous computer applications but a good operator can reach speeds of over 50 words per minute! There are other digital modes such at FT4, FT8, JT9, Q65 and others. Even radio teletype (RTTY) is a digital mode which was in commercial use in the US as early as 1932. Amateur radio operators use the following frequencies:

• 1.8 - 2 MHz ("160 meters")

• 3.5 - 4 MHz ("80 meters")

• 5.33 - 5.4 MHz ("60 meters")

• 7 - 7.3 MHz ("40 meters")

• 10.1 - 10.15 MHz ("30 meters")

• 14 - 14.35 MHz ("20 meters")

• 18.068 - 18.168 MHz ("17 meters")

• 21 - 21.45 MHz ("15 meters")

• 24.89 - 24.99 MHz ("12 meters")

• 28 - 29.7 MHz ("10 meters")

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🕵️‍♂️ CLANDESTINE

Because shortwave equipment is easy to purchase or build, it’s occasionally used for illicit or unauthorized communications. In the western hemisphere, you’ll often hear Spanish-speaking individuals carrying on personal conversations in sideband mode — commonly referred to as “Echo Charlie” operations. These typically fall in the 6.52–6.8 MHz range and often use modified amateur radio gear.

📻 Pirate Radio

There’s also a lively world of pirate broadcasters, many of whom operate in the 6.885–6.965 MHz range — especially around 6.925 MHz. These stations often feature music, commentary, or satire, and are a favorite among shortwave DXers.

🚫 Government Jamming

Some governments use shortwave to jam foreign broadcasts, attempting to block propaganda or dissenting views. One example: Cuba’s infamous “bubble jammer” (named for its bubbling-water sound), which was frequently heard on 6.03 MHz targeting Radio Martí. (Status of that jammer today is uncertain.)

🕵️‍♀️ Numbers Stations

Shortwave is also used by spy networks due to its global reach and the concealable nature of receivers. These transmissions often take the form of “numbers stations”, which broadcast long strings of numbers (usually in groups of five) in English or Spanish — sometimes via Morse code or other formats.

Heavy users include:

• United States

• United Kingdom

• Cuba

• Israel

These stations rarely follow fixed schedules or frequencies — though Cuban spy broadcasts are known for their predictability. If you stumble across a voice reading numbers in a steady rhythm, you’ve likely found one.

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📡 OTHER SERVICES

Numerous other services make use of the shortwave spectrum beyond traditional broadcasting and amateur radio. One example is Rutgers University's CODAR system, which measures ocean wave height and transmits around 4.9 MHz each evening.

• In AM mode, it sounds like a series of beeps.

• In sideband mode, it produces a distinctive “shwoop – shwoop – shwoop” sound.

Other users include the federal government, the Red Cross, and various emergency and research organizations — all relying on shortwave for long-distance, reliable communication.

🚫 Unlicensed Use

Shortwave also sees unlicensed activity, including:

• CB operators who transmit outside the legal 26.965–27.405 MHz range to make illicit long-distance contacts.

• “Peskies” — typically Spanish-speaking individuals engaging in CB-style conversations around 6.8–7.0 MHz.

The nickname comes from “pescaderos” (fishermen), as many were believed to be maritime operators.

CB users may use AM, FM, or sideband, while peskies almost exclusively use sideband mode.

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