Mysterious signals from West Africa on 28 MHz

Discussion in 'Amateur Radio News' started by G4TUT, Sep 11, 2019.

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  1. KD7WPJ

    KD7WPJ Ham Member QRZ Page

    It is possible that those signals generated by Russia's Wagner mercenaries...
    K0UO likes this.
  2. KQ6XA

    KQ6XA Ham Member QRZ Page

    Propagation to the IARU R1 monitor DK2OM from Gabon, was most likely combined Sporadic E (Es) and some common TEP in the equatorial Africa region.
    2019 is a peak year for Es propagation, and the Sporadic E this summer in Europe was very strong.

    In my experience, the most likely source of the signal is actually quite mundane:
    It is a simple low power telemetry transmitter at a remote site.

    These types of utility RF links are commonly utilized for monitoring the status of remote pumps, fluid levels, generators, or other types of remote infrastructure devices.

    They are more common in the High Band VHF and UHF range, but older units were often in Low Band VHF and 27 MHz.
    I don't think it is unusual to see such a signal in the 28 MHz band.
    After all, most hams aren't really using that part of the 10 metre band much :) so it is a relatively clear frequency.
    The 25 to 40 MHz part of the spectrum is a good choice for low power remote telemetry in the kind of terrain found in Gabon.

    If it was originally set up on solar power, at this point in time, it could be a zombie transmitter! (not maintained, not utilized for original purpose, but still transmitting).
    Likely a converted crystal-controlled CB radio repurposed as a cheap telemetry transmitter.

    I derived the following info from the waterfall plot:

    • AM transmitter carrier drifts when it is first keyed (normal for older crystal controlled gear).
    • AM pulse modulated with a 494.5Hz tone (within the common range for telemetry).
    • Rate of pulsed modulation = 201.7 milliseconds (or 4.9 dits per second).
    • Harmonic content of modulation indicates the modulation tone is square wave or clipped sine wave.

    The waterfall plot in the IARU-R1 Monitoring Report, shows the characteristics:

    Last edited: Sep 12, 2019
    KD2KIQ, WA9ROB, AF8CF and 9 others like this.
  3. KE9OL

    KE9OL Premium Subscriber QRZ Page

    NL7W and K0GOV like this.
  4. KB7AA

    KB7AA Ham Member QRZ Page

    Me too! And I dont have any radios!!
  5. K4XJ

    K4XJ Ham Member QRZ Page

    I'm hearing that old woodpecker sound like we use to hear back in the 1980'sand 1990's on the 60 meter band. Every night on 5.371.50 and 5.403.50 it will alternate between these 2 channels. Yes we share the 60 meter band with military and government agencies, but this sounds exactly like the old Russian woodpecker!
  6. WZ7U

    WZ7U Ham Member QRZ Page

    I thought the term JOB stood for Just Over Broke
  7. DJ7WL

    DJ7WL Ham Member QRZ Page

    We here in Germany listen for that signal in 10 M band longer time ago. We investigate and finally we found out, this signal have been produced by fisherman. They marked her fishing net with a transmitter in the 10 M band. With a direction finder later on the find the net again. So maby you test it also in this direction. VY 73 Joachim from Hamburg Germany
    WF7BSR, SA6CKE, KE9OL and 1 other person like this.
  8. W0PV

    W0PV Ham Member QRZ Page

    Driftnet buoy beacons have been observed for a long time, sometimes (illegally) intruding on amateur bands, including 10 meters. Heard in FL quite prominently on 160m too.
    KE9OL likes this.
  9. KA2FIR

    KA2FIR Ham Member QRZ Page

    I've been hearing it across the 40M band nightly now.
    K4XJ likes this.
  10. N5XKG

    N5XKG Ham Member QRZ Page

    I was hearing it around 7.074 (I think) last night about 04-5z. Showed up nicely on the waterfall display.

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