Can you help Rick ID this mystery digital signal?


Photo from Rick’s location in Vernon, BC.

Many thanks to SWLing Post reader, Rick Slobodian, who writes to request help with the following:

Tecsun-PL-606I was on the beach at our lake, [where I was listening to my] Tecsun PL-606 receiver.

[On Friday, August 19, 2016 at 1800 UTC, I noted a] “beeper”: beeps at Hz repetition rate , does not appear to be data, it beeps for about a minute then there is a short data burst then beeping again for a minute or two.

This went on for over an hour.

Location of Vernon, British Columbia, Canada.

Location of Vernon, British Columbia, Canada (click to enlarge).

[The beeping covered] all frequencies between 13400-13800 kHz. [Then on August 20, it started at] start 1745 UTC and was no longer on 3400-13800 but now on
all frequencies between 12120 -12250.

What is it? [Take a listen:]

Click here to download a recording of the beeping.

My ham radio friend says there are a network of stations that send out pings that everyone in the group transmits and everyone receives. The signal strength and phase of the rx signal is correlated at each receiver station, to direction find some unknown station.

Was there such a thing during the cold war, and is it still around? What is this system and where can I find out more about it?

Thanks for your inquiry, Rick. This is outside the scope of what I understand on the HF bands, so I hope SWLing Post readers can chime in and offer suggestions.

Please comment if you can help Rick ID this transmission!

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14 thoughts on “Can you help Rick ID this mystery digital signal?

    1. Devotech

      I hear it also in Wisconsin USA. It starts at 13500 and races down to 13400 each “beep”. Nothing like nickarr’s video. It is a sweep down the frequency range. I lost it tonight around 4:00 UTC, but it was there most of the day.

  1. Walt

    I’m looking at it right now (23:50 UTC). It’s broadband between 13390 and 13600 or so, and continuous. I know CODAR well, and unless there are several types, then I’m not 100% certain. Instead, I’m thinking that one should consider military OTH radar. I do see these often in the higher frequencies, but they do tend to be shorter bursts, and variable in width and frequency. Either way, it’s one of the two!

  2. Brendan WA7HL

    That is indeed CODAR, a form of radar that measures wave height. Sounds like AM mode to me, try it in SSB if possible to hear the sweep. I don’t like it much, as it covers large portions of HF that don’t need to be interfered with.

  3. Ken

    After chasing WEFAX DX for 30+ year I can say it is not WEFAX. It does sound a bit like the start of a WEFAX transmission that never really “starts”.

    Rick, are you sure it’s not the Ogopogo tracking sounder from Lake OK? 🙂

  4. DL4NO

    * An AM demodulation suppresses lots of information the signal might have contained.

    * A beep at regular intervals contains not much information…

    * This could easily be some spurious emission from any electronic device. Such beeps are quite typical for battery chargers when the battery is full.

    * 13.553 MHz to 13.567 MHz is an ISM band used for RFID devices and such.

  5. Rich

    I’m pretty sure it is a weather fax (WEFAX) signal and the frequency range is about right. Since you were using a PL-606 in AM mode the signal would have seemed quite wide and the WEFAX signal is wide as well, 3000 Hz. A search for WEFAX frequencies will give you times, frequencies, etc. It’s very easy to decode but you will need a SSB receiver.

    Further info.

    1. Tom Servo

      Aaron gets a gold star! That’s exactly what that is. I hear this same thing 24/7 on 4 and 13 MHz, and have found one of the transmitter sites at my local beach.


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