While composing another message I had an idea that might help reduce
FT-8 congestion.

Every FT-8 receiver listens to an entire "band" (approximately 1 SSB
bandwidth) and it will hear and decode every station transmitting
anywhere in it. This makes each station's exact transmit frequency
unimportant. So for some time I've felt that FT-8 transmissions should
be randomized in frequency to avoid repeated collisions, as most WSPR
stations already do. But the transmit frequency need not be truly
random; if it is based on a hash function, then other stations can know
the frequency on which you will (or would) transmit during any given
15-second slot.

So here's my idea. Divide the FT-8 "band" into slots, each wide enough
to take one signal. Set your transmit frequency "slot" based on a hash
of the transmitting station's callsign, perturbed by the time of day in
15 second increments. This sets up the frequency hopping. It is backward
compatible with current operation.

Everyone monitors everyone else's protocol exchanges so they are aware
of the active callsigns and their current QSO exchange states. If your
hash happens to match that of a station expected to transmit, either
inhibit transmission or choose from a small set of secondary "overflow"
slots unprotected against a collision.

I just had this idea so it is far from fully formed. Nor can it be
perfect because, if nothing else, you are unable to monitor
transmissions while you yourself are transmitting. But I wanted to see
if anyone else had any comments on it, or if it has been suggested before.

73, Phil





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