al's brief shortwave radio listening guide

What's on shortwave radios?

A shortwave radio provides unique and extraordinary access to worldwide communications. With a relatively simple antenna, it is possible to listen to international broadcasts, ships at sea, transatlantic airliners, military stations, even international spies!

It is impossible to cover the entire shortwave listening hobby on a single web page (especially when it comes to more complicated antennas, and proper lightning safety systems). This information is therefore severely limited. However, if you have any questions after reading this guide, I'd be happy to answer them - feel free to email me (kc2klc@lutins.net) and I will try to help.

There are basically two types of signals on shortwave radio: voice and data.


All shortwave receivers will pick up voice communications that use "AM" mode, but for most types of voice communication (with the exception of international broadcast stations) you will need a radio with sideband mode (it may be labeled SSB, BFO, CW, or LSB/USB). If you're tuning around and hear an unintelligible voice (sounds like Donald Duck, or the parents in the Peanuts cartoons), that's sideband. If your radio has "upper sideband" and "lower sideband" settings, you may need to try each, and tune around a bit, to figure out which setting works for that transmission.


Most of the sounds (beeps, squeeks, screeches and squawks) you will hear are data signals. Some of these can be decoded using a computer and inexpensive software, but some are encrypted (and therefore cannot be decoded), while others require very expensive software. A growing number of these are continuous or intermittent growling sounds that consist of encrypted voice or over-the-horizon radar signals; there is no way to decode these. But there are digital signals that can be decoded by connecting the radio's headphone jack (or "line out" jack if your radio has one) to the "line in" or "microphone" jack on you computer. You will need to keep the radio volume low. If there is no "line in" jack on your computer, it may be possible to use the microphone jack, but you will have to turn the radio volume down very low. Examples of signals that can be decoded are weather maps sent via facsimile to ships at sea, and messages sent to aircraft on international flights.

What it takes to receive shortwave signals

You will, of course, require a radio that receives signals in the "shortwave" (3 - 30 MHz) portion of the radio spectrum. There are plenty of standalone receivers that can do this, but a popular solution these days is a software defined radio. These are available inexpensively, but they require a computer to be connected to the receiver.

You will also need a decent antenna to receive worldwide shortwave signals (in other words, something a bit better than the telescoping "whip" antenna that may have come with your radio). Luckily, you don't need anything fancy - a long piece of wire strung between your house and a tree or pole will do just fine. It's best if the majority of your wire antenna is located away from your house, so as to minimize interference from home appliances. About 20-40 feet (6-12 meters) of wire is generally sufficient; if you're in a rural area, double that is even better (in urban areas interference can overwhelm longer wire antennas). Running one end through a window or into a hole in the wall directly to your radio will produce acceptable results, but make sure to leave it unplugged from the radio unless you're using it - the static that can build up in the wire from wind, rain or snow can damage the sensitive electronic components in some (especially newer) radios. This also provides some protection from lightning, but ideally you should have your wire antenna connected to a ground rod through a lightning protection device.

The other major factor affecting your reception of shortwave signals is called propagation. Propagation refers to the atmospheric conditions that affect radio reception. In addition, your elevation, the time of day, the season, even conditions on the sun (including solar storms and the sunspot count) all affect radio reception. In general, during the day the higher portion of the shortwave dial (above 10 MHz) is most active, while at night the lower portion (below 10 MHz) is most active. Winter is much better for long-distance reception than summer, and periods of high sunspot count help as well. The higher your elevation the better, but this is not a critical element. Do not use your radio during a thunderstorm - even if your antenna is not hit directly, lightning can induce large enough electrical charges into your wire antenna to fry your radio!

Types of signals

The following list outlines signals that a beginner will most easily be able to receive:


Many countries operate "standards" stations so that the time and frequency can be measured precisely. The U.S. National Institute of Standards and Technology runs two such stations, WWV (Colorado) and WWVH (in Hawaii). Both stations operate on 2.5, 5, 10, 15 and 20 MHz, and are easy to hear because they operate at very high power. These stations provide the shortwave listener with three useful functions:

WWV has a male voice announcing the minutes, while WWVH has a female voice, so that you can tell them apart. These stations operate in "AM" mode so you do not need a radio equipped with sideband capability to receive them.

Many other countries operate standards stations as well; in North America, Canada's CHU can often be heard on 3.33, 7.85 and/or 14.67 MHz. I've occasionally heard HD2IOA in Ecuador on 3.81 MHz, and sometimes LOL in Buenos Aires, Argentina or PPU in Rio de Janeiro, Brazil on 10 MHz (when WWV was coming in weaker) from my home in upstate New York.


International broadcasters use high power and "AM" mode, and so are also very easy to receive. If you tune around a shortwave radio randomly you will hear them - they sound just like AM and FM radio stations, except that they may be in foreign languages. At one time just about every country had a shortwave broadcast service, but due to budget cuts and a shrinking audience a lot of these stations are being shut down. There are still plenty left, though, and you can listen to broadcasts from countries very far from you (many broadcast in English). Shortwave broadcasters are a wonderful source of news (often with a very different slant from the one you're used to) and music from around the globe.

These are some of the popular frequencies used by International broadcasters:

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


Airplanes use VHF (not shortwave) radios for most of their communications, but when traveling far out over the ocean they need to use shortwave radios because of their superior ability to transmit long distances. There are a number of MWAR (Major World Air Route) and LDOC (Long Distance Operations Controls) stations throughout the shortwave dial that can be heard around world. There are also "Volmet" stations that broadcast nothing but weather conditions to pilots worldwide. Most aviation communications can be found in the following frequency ranges:

The most commonly heard in northeastern North America include:

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


Like airplanes, ships need to switch from their short-range VHF radios to long-range shortwave radios when they're far out at sea. Ship-to-ship and ship-to-shore communications also use sideband mode, most commonly in the ranges of 4.35-4.44 MHz & 6.2-6.5 MHz. Unfortunately for the shortwave listener, a lot of maritime communication is being converted to encrypted digital transmissions which cannot be decoded by third parties.

There are also stations devoted to providing ships with information on conditions at sea, such as wave height, the presence of icebergs, storms, and other hazards, etc. These also operate in sideband mode. The most commonly heard in northeastern North America are: 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. I've never had the fortune to hear a distress call in person, but you may want to park your radio on one of these from time to time - you never know!


Although most military communications use encrypted digital modes these days, voice communications in the clear (again, sideband mode) are still out there. The easiest to receive in the eastern U.S. are: These signals (as well as maritime voice signals) require single-sideband capablity.


CB operators (mostly truckers) use a portion of the shortwave "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 busiest frequency is 27.185 MHz, which is Channel 19.

Amateur ("ham") radio operators are major users of shortwave radio. Most talk using sideband mode, and many still use morse code (because it typically reaches farther than voice), which can be decrypted by numerous computer applications (my favorite is CWGet, available from DXSoft). Amateur radio operators use the following frequencies:


Since shortwave equipment is easy to purchase or build, there are a number of people who use it for illicit purposes. In the western hemisphere you will frequently hear There are a number of "pirate" radio broadcasters on the air, most commonly in the 6.8 - 7 MHz range. They frequently use 6.925, 6.930 an 6.950 MHz.

Various governments also utilize the shortwave spectrum for nefarius purposes. One is to jam the broadcasts of other countries' stations in an attempt to keep propaganda from reaching its intended audience. I used to frequently hear a "bubble" jammer (so called because it sounds like bubbling water) used by Cuba on 6.03 MHz used to jam the U.S.'s Radio Martí broadcasts (I don't know if they're still active on that frequency).

There are also active spy networks using shortwave radios (because the radio signals reach around the world, and the radios can be easily concealed). Most consist of "numbers" stations, broadcasting strings of numbers (typically in groups of five), often in English or Spanish. The U.S., England, Cuba and Israel are all heavy users of numbers stations. Since they are clandestine, they do not generally stick to particular frequencies or schedules (although Cuba's spies are often on quite predictable schedules!), but if you're ever perusing the dial and come across a voice (usually sideband; sometimes AM) that's simply reading a long list of numbers in groups, you've found a numbers station (they also use other formats, like morse code).


Numerous other services make use of the shortwave spectrum. Here in upstate New York I pick up Rutgers University's CODAR system (for measuring ocean wave height) around 4.9 MHz every evening (in AM mode it beeps; in sideband mode it goes "shwoop - shwoop - shwoop"). The federal government, the Red Cross, and numerous other groups also use shortwave radios.

There is also unlicensed use of the shortwave bands. Some CB radio users operate outside their designated frequency range in order to make illicit long-distance contacts (the practice is called "feebanding"). There are also "peskies", usually speaking Spanish, who engage in CB-like conversations (often around 6.8 - 7.0 MHz - the same range where pirate broadcasters operate; they are so named because they originally started as, or were though to be, "pescaderos", or fishermen). The CB operators use both AM and single sideband, whereas the peskies use sideband almost exclusively.

For additional information regarding shortwave listening (as well as other radio monitoring hobbies), I highly recommend The Spectrum Monitor, which offers electronic (PDF format) subscriptions.

Communicating using shortwave radio

You are not limited to simply listening in on shortwave signals - you can, if you obtain an amateur radio license, use shortwave radio to communicate with people all around the world, using voice and various data modes. (You can also operate portable "walkie-talkie"-type radios in the VHF/UHF spectrum, and even communicate using satellites!) Obtaining an amateur radio license is not terribly difficult - one needs only to pass a 35-question exam covering basic electronic theory and FCC regulations. The Amateur Radio Relay League (ARRL) offers a complete guide to obtaining a beginner's (Technician-class) license, the ARRL Ham Radio License Manual which (in addition to covering each required topic in-depth) contains the entire pool of questions (with answers) from which the test is drawn.

last updated 2 March 2023

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