Unknown signal in VHF.

  • Hello people...


    I was checking TO-108 (or CSS6?), when I noticed a 'floater', a signal rapidly changing over a wide range of the 2m band. It doesn't seem to be local signal, but neither does it fit any satellite I could identify. The following cycle repeats with large variability...:

    - The signal starts at the high end of the range (variable)

    - scans downwards, quite rapidly, and at a variable rate

    - at some point I seem to have detected 'hum' on the signal which would indicate 'terrestrial' origin, I guess

    - at several points in the scan, the frequency abruptly jumps

    - signal strength is variable - though not very strong.

    - frequency starts at about 146 MHz and stop before 144 - quite variable also.

    - As I received the signal for more than my 15 minute max window for LEO sats, I'm doubting it's actually a satellite. On the other hand, I can't find a logical behaviour for the rest)


    I've include an example screenshot (note that most recent signal is at the top :) :

  • Hello John


    I observed also mysterius signals in the 2m band. The most is self made local QRM from PC, VDSL-modem, TV, aso. I see also such signals on your screenshot, the vertical ones. But this signal you are talk about is really mysterius. If you run your RX with a battery, you can eventually exclude local QRM. If this signal is received clearly via antenna, then it is external QRM. Evtl. helps the site https://qrm.guru/


    Good luck

  • Hello John


    If you run your RX with a battery, you can eventually exclude local QRM. If this signal is received clearly via antenna, then it is external QRM. Evtl. helps the site hthettps://qrm.guru/

    Removing the antenna make the signals disappear completely. I have bookmarked the internal - known - QRM signals so I can recognize those easily. The randomness, and variable signal level make me quite sure it is not a local. I haven't eliminated intermodulation yet. I have quite a few very strong FM transmitters near. But the IM signal should have the modulation of the FM, which is not the case. Guess what - at the moment I can't find the signal ... I'll have another go tomorrow.


    Thanks for the QRMGURU link, That may come in handy.


    Cheers!