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How do WSPR signals avoid frequency collisions?

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Submitted ⁨⁨5⁩ ⁨weeks⁩ ago⁩ by ⁨einfach_orangensaft@sh.itjust.works⁩ to ⁨amateur_radio@lemmy.radio⁩

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  • yo3gnd@lemmy.radio ⁨1⁩ ⁨week⁩ ago

    They don’t.

    You randomly position yourself somewhere in the tiny sliver of a sub-band, and TX. An important bit of WSPR operation is to only transmit in 10-20% of the windows, not all of them. I guess it is a form of poor man’s TDMA.

    Another trick, also used by FT8 SWL mode: you decode a batch of signals, you regenerate their audio and subtract that from your RXed audio. This is called a pass. Repeat for a few passes, decode after each.

    Hidden signals discovered like this are not perfect and rely heavily on FEC, especially if something else masks them, but hey do show up.

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    • einfach_orangensaft@sh.itjust.works ⁨1⁩ ⁨week⁩ ago

      Thx for the answer, also very interesting, never heard about that FT8 audio subtraction method before but makes total sense :D

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  • slazer2au@lemmy.world ⁨5⁩ ⁨weeks⁩ ago

    My assumption would be it has some form of dynamic frequency selection algorithm so it sits there and listens for a bit to find an employee channel and uses it for broadcast.

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