Category Archives: Beacons

Bob’s Radio Corner: Tuning Single-Letter Cluster Beacons

Source: Better Shortwave Reception, William I. Orr, W6SAI, Radio Publications Inc., Wilton, CT, 1st Edition, p. 25, 1957.

Tuning Single-Letter Cluster Beacons

by Bob Colegrove

Part of the allure of shortwave listening for me has always been vicarious visits to “those faraway places with the strange-soundin’ names.”  After one has logged several big-time broadcasters, one begins to look for new challenges.  Most of the so-called “utility” content which once occupied the space between the broadcasters and hams is now a vast open desert interrupted only with an occasional digital buzzsaw, a wide-band CODAR experiment, or some RTTY.  But now and then you come across a signal that grabs your interest.  In this case it happens to be a group of signals referred to as the Russian single-letter beacons.  A good introduction to these beacons is here

https://en.wikipedia.org/wiki/Letter_beacon

and here

https://www.hfunderground.com/wiki/Letter_beacon.

After many years, there is still some speculation as to the history, purpose and power of the single-letter beacons.  Rather than repeat what has already been said, this posting focuses on my technique for monitoring a subset of these beacons called “cluster beacons.”  They are called that because they are grouped close together, just 100 Hz apart, at ten different locations across the shortwave spectrum.  A good tabular summary is at https://priyom.org/military-stations/russia/single-letter-beacons.  Some stations may not currently be broadcasting or may be on at selected times.

These stations will neither captivate you with content or readily QSL.  They are all continuous wave (CW) and are thus heard by turning on your radio’s beat frequency oscillator (BFO) or selectable sideband (SSB) detector.  I am Morse-code-challenged – always have been.  Fortunately, these stations all broadcast their single letter dits and dahs repeatedly and slowly.  Having relatively low power, the challenge here on the East Coast of North America is just to pick them up through the band noise.  Some nights are better, some not so good.

For purposes of this posting, I have focused on the stations around 7508 kHz.  This seems to be the best cluster, at least at the current time and location.  “D” is invariably the strongest and most consistent, with “P,” “S,” “C,” and “A” fading in and out at different times depending on the propagation.

To tune through the cluster, first tighten up your selectivity as narrow as possible – 500 Hz if you have it.  Use the fine-tuning control – 10 Hz if you have it.  The best way to catch these beacons is to sneak up on them.

  • Approach upward from the low side of the cluster using USB, start tuning around 7508.3; or
  • Approach downward from the high side of the cluster using LSB, start tuning around 7509.5.
  • Try tuning in both USB and LSB to determine the better reception of the signal you are trying to hear.

Depending on which signals are audible, you may hear two or three making it through the 500 Hz filter at the same time, each with a different pitch.  The beacons will change pitch as you approach, going from a high pitch heterodyne to a lower pitch.  When you reach zero beat with a station you will be directly on its frequency.  Zero-beating a strong signal may help you hear a weaker one.  Tables 1 and 2 show how this works for USB and LSB respectively.  They indicate the heterodyne tone you will hear as you tune towards or away from each signal.

The negative value tones in the tables may not be heard if you are using a radio with selectable sideband (SSB).  If your radio has a traditional BFO, you will hear a tone at either side of zero beat.  In the tables, interpret the negative numbers for their absolute value, for example, |-100 Hz| = 100 Hz.

As part of the challenge for the 7508 kHz cluster, you may have to contend with interference from WRNO, 7505 kHz.  When you finish this challenge, try it again on the 10781 kHz cluster.

Good DXing.

Mario reminds us to log 10 meter CW beacon activity!

Many thanks to SWLing Post contributor, Mario Filippi (N2HUN), who shares the following guest post:


Ten meter beacon band spans 28.100 – 28.300 MHz (photo by author)

Recent 10 Meter CW Beacon Activity

Mario Filippi, N2HUN

The 10m band has been coming alive lately and it’s time for all hams and SWLs to take advantage of it.  For several years I’ve been listening to 10m beacons with mediocre results but this has all changed over the past few days with loggings of European beacons running as low as seven watts.

These amateur radio beacons can be found from 28.1 – 28.3 MHz, sending out their callsigns in CW along with other information such as power output, grid square, antenna type and other tidbits of interesting information.  Most USA beacons are heard from 28.1 – 28.2 MHz while international ones inhabit 28.2 – 28.3 MHz. Some beacon ops will request QSL card reports the old school way via mail. I’ve written out a few already, bringing back fond memories of my early days as a ham and SWL.

Over the past few days at my central NJ QTH, using an Airspy HF+ Discovery and a ground mounted 31 foot vertical, here are some of the DX beacons logged:

  • IZ8RVA, 28.239 MHz, 1230 UTC
  • OH9TEN, 28.265 MHz, 1253 UTC
  • LA5TEN, 28.237 MHZ, 1300 UTC
  • OK1AR, 28.249 MHz, 1214 UTC
  • DA5TEN, 28.237 MHz, 1219 UTC (7 watts, vertical antenna!)
  • DL0IGI, 28.204 MHz, 1251 GMT (50watts)

Note that most signals were 449 with QSB so a quiet room, a good pair of headphones, many cups of good hot coffee/tea and a heap of patience are needed.  Beacons will send a continuous CW tone as a preamble while others will transmit a series of V’s (…-).  So, spin that VFO dial up to 10 meters, a band which comes alive as sunspots rise.  If you are a QRP’er, this comes as good news since this band is great for those who love to run peanut whistles.

Thanks and have fun!

Solid copy: Tom receives JG2XA in the Netherlands on his PL-365

CountyComm GP5/SSB, aka Tecsun PL-to 365

Many thanks to SWLing Post contributor, Tom Kamp (PA/DF5JL), who shares the following brief report and video:

Today (September 21, 2022) around 2015 UT strong signal on 5006 kHz (CF) from JG2XA beacon from Japan (0.2 kW) near Den Helder, in North-Holland, The Netherlands.

JG2XA transmits continuously at 200 W on 5006 kHz and 8006 kHz. The type of radio signal is H2A (amplitude modulation with coded tones in the single sideband).

Received with the Tecsun PL-368 and the built-in telescopic antenna! The dBm display of the unit is very inaccurate (in USB), yet S5-S7 should be rated appropriately. Top signal, top RX ?

73 Tom Kamp PA/DF5JL

That’s quite a catch for the PL-365. Thanks for sharing this, Tom!

Guest Post: 13dka Explores the International Beacon Project

Many thanks to SWLing Post contributor, 13dka, who shares the following guest post:


In search of benchmark signals: The International Beacon Project

by 13dka

If you – like yours truly – like to tinker with antennas and radios to get the most out of them, you likely have your own set of reference stations. If this is a new concept for you – reference stations are whatever stations you deem apt to check propagation, the general function of your radio, when trying to improve reception or comparing radios… They are ideally always on when you need them and come in various strengths and distances on several bands from all over the world. Traditional sources for that are of course time signals and VOLMET stations on HF, even though the latter are giving you only two 5-minute slots per hour for testing reception from a specific region and the former have their own specialities here in Europe:

Audio Player

A typical scene on 10 MHz, captured at home 30 minutes after the full hour: BPM voice ID from China mixed with something else, then Italcable Italy kicks in on top of some faint murmur possibly from Ft. Collins, in winter some South American time stations may stack up on that together with splatter from RWM 4 kHz lower…

A reliable source of grassroots weak signals is particularly desirable for me because I enjoy proving and comparing the practical performance of radios at “the dike”, a QRM-free place on the German North Sea coast. In the absence of manmade noise and the presence of an ocean adding 10dB of antenna gain, finding benchmark stations with “grassroots” signal levels turned out to be a different challenge than it used to be: With somewhat sizeable antennas the stations tend to be (too) loud there, even with the baseline ionospheric conditions under a spotless sun in its activity minimum. In short, my old benchmark stations didn’t work so well anymore and I had to find something new. Continue reading