NDB DX is an aspect of our radio hobby where you listen for distant non-directional beacons on medium and long waves. Most countries are phasing these out over the next decade.
Non-directional beacons, or NDB, have been a mainstay of aircraft navigation since the 1930’s. Soon, you will notice they have gone silent in favor of more modern VOR and, especially, GPS. Try NDB DX while you can. As a motivation, I asked Steve AA7U to write this guest article.
“I’ve been listening for LF NDBs (non directional beacons) since the 1980s and still enjoy listening for them. NDBs are generally associated with the airport they serve and are used for aircraft navigation, where the plane has a receiver specially designed for NDB reception. You will find NDB in the 200-530 kHz frequency range, mostly 200-430 kHz. They send a two or three letter (sometimes with a number) Morse code identifier with a short pause then repeating, over and over, non-stop.
The ident is usually an abbreviation of the airport or a local geographic feature. Signal can be heard in AM mode, with a carrier and (in the US) a lower and upper sideband that carries the modulated identification at 400 or 1020 Hz. Canada uses a carrier and an upper sideband ident. Most US beacons run 25-50 watts, with a few with 400 watts; many Canadians run much more power, 250-1000 watts.
Similar to AMBC stations, daytime reception is limited to ground wave. But at night, NDB DX carries to 1500 miles or more, depending on solar conditions, storm static and beacon power. The past several years has seen many NDBs turned off and decommissioned due to political interests that claim GPS is all that is needed for aircraft navigation. Canada has a current official schedule of turning off beacons that will end with almost all LF beacons turned off in the next several years. US has no official schedule but seems to be following suit. Some Alaskan beacons will remain on as there are still bush pilots relying on them. The rest of the world has not been quite so quick to turn NDBs off, though more and more are being turned off.”
Most NDB transmitters use short, top loaded vertical antennas, as shown above. Here is a video which explains NDB and related direction finding.
NDB DX on Your Radio
“There are a few DXers such as myself who try to hear as many beacons as possible, especially ones far away. There is a group list with members worldwide, where we post our catches. Several members maintain a free beacon list, one for Europe, one for North America, one for rest of the world. Here is an example.
Most NDB DXers progress from using basic gear and not knowing much, to gradually advancing to better gear and learning about how to better receive LF signals—at least that was the way I did it. I started with a basic homebrew active whip and a Kenwood R70 receiver which had a CW filter already built in. Eventually I learned about external narrow audio filters which I built and which helped with weak signals. When I retired in 2001 I moved back home to the folk’s rural place in north east Oregon and had a 1600’ E/W longwire. Being a quiet location and also the solar minimum, I heard lots of Pacific beacons, some that no one else in North America had ever heard before. That will probably be the best antenna for LF reception I’ll ever have.
Several moves later I’m now in southern Arizona living on my brother’s property in the desert—I’m fortunate to be able to have a 900’ E/W longwire and a 700’ N/S longwire; it’s not nearly as quiet here but I can still hear some good beacons now and then. Those are my main antennas for LF reception but I experiment with small 3-10 foot diameter loops and various loop amps both homebrew and commercial.
Local AC noise is the main problem most folks have if they want to try to hear anything at LF and of course it keeps getting worse for most folks, with the proliferation of all the electronic gadgets that spew interference, especially bad at LF. It can be carried by the powerlines, in which case there is usually little that can be done about it. I have occasional bad noise carried by the powerlines that wipes out all LF listening—sometimes it’s lasted as long as several weeks before suddenly stopping.”