I have mostly only used non-crowded 2 meter repeaters, but recently I tuned my radio to the downlink frequency: 437.8 mhz while the ISS was passing overhead - just to listen.

What I heard was people calling out their call signs in phonetic alphabet, that is all, and no real space between calls.

So what's the procedure?


1 Answer 1


Same as any other FM satellite, which... yeah, is hectic. FM satellites only have one "channel" for everyone in the footprint, passes are short, and if you want to work as far as possible, that means catching people in the brief time when the bird is setting for them and rising for you, or vice versa.

So the protocol is pretty much just callsigns and grid squares:

(Calling): "KC2G FN21"
(Answering): "KC2G W9ABC EN61"
(End of QSO): "QSL!"

except with frequently lots of people trying to talk over each other, which doesn't work great on FM. And then someone else puts their call out there, or sometimes tries to call one of the people who made the previous QSO. Sometimes someone loses the signal or has radio trouble... if they don't answer within a few seconds, there's a good chance someone else will jump in.

It's chaotic, a bit intimidating, and not a good venue for a rag chew. If you try during really odd hours it might be calmer, though.

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    $\begingroup$ (and get used to everyone in eastern North America saying "fox" instead of "foxtrot". We can't afford the extra quarter second!) $\endgroup$ Commented Aug 17, 2023 at 18:19

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