FT8 anomaly or long delayed echo?

My friend Alf, LA2NTA, has sent med these screenshots from when he has been operating FT8. The first image is when operating 10 meters and took place early in November.

Two of LA2NTA CQs being received by himself on 10 meter (in red)

It shows how his own CQ comes back to him at 10.54.00 and at 11.00.00 and is decoded in his own receiver.

The second example is from 20 meters and took place just a few days ago.

LA2NTA CQ being received by himself on 20 meter (in red)

For the first example he also took an image of the spectral display. It shows lots of repeated noise burst all over the FT8 band.
FT8 band on 10 meters showing some form of noise all over the band
It is hard to explain this, but my hunch is that it is something local and not a propagation phenomenon, but who knows?

Sverre Holm, LA3ZA, is a regular contributor to AmateurRadio.com and writes from Norway. Contact him at [email protected].

5 Responses to “FT8 anomaly or long delayed echo?”

  • Brian VK2AAF:

    Someone is pirating LA2NTA’s callsign.

  • Simon G0FCU:

    The screenshots show the received signal with the same timestamp as when he was transmitting. As the timestamp is not included in the wspr message this is a local problem.

  • W3cde:

    Around 1967 this was common at night on 20M. Both on ssb and Cw

  • Vidas N8AUM:

    I get that sometimes to and isn’t limited to just this mode, has to with buffering? My best guess is the some buffer isn’t empty when the receive cycle begins.

  • MW1CFN:

    My wsjt program displays my own cq in the RX window when it reaches the tx limit. That is certainly a bug, and sound like it’s related to the op problem.

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