so ive been doing terrestrial stuff for years, mostly HF, but finally got curious about working through the LEO satellites after watching a video of someone working SO-50 with just a handheld. that got me down a rabbit hole and now im more interested in the linear transponder birds like FO-29 or AO-73 rather than the FM ones because honestly the FM ones seem like they'd get pretty crowded fast.

my question is mainly about the doppler correction situation. i understand the concept — the satellite is moving toward you so the frequency shifts up on downlink, away from you shifts down, all that. but in practice do people just manually tune while they're in the pass or do you actually set up software to do it automatically. i have a IC-9700 so i think it can be CAT controlled but ive never set that up for anything moving before. also using a fixed yagi right now, not a tracking mount, is that going to be a total dead end for linear transponder work or can you make it work if the pass geometry is decent.

any advice appreciated, been lurking this forum for a while and you guys seem to know your stuff

the doppler thing is very manageable once you get used to it, especially on something like FO-29 where the transponder passband is fairly wide and you have some wiggle room. most people i know use either Gpredict or MacDoppler and just let the software push corrections to the radio via CAT. with the 9700 you should be in pretty good shape, it plays nice with most of the common sat software. just takes a bit of setup to get the CAT connection dialed in but once it's working it's mostly hands off for doppler, then you can focus on actually finding the passband and not losing the other station mid-QSO which is the harder part honestly.

the fixed yagi is going to limit you but it's not a complete dead end. you want passes that go reasonably high overhead for your direction of aim, and you'll get a usable window. guys have made contacts with fixed antennas, it just takes more patience and you're not going to work the low elevation stuff at all. if you get hooked on this you'll end up wanting az/el eventually, fair warning.

yeah what he said about Gpredict, that's what i started with and still use. one thing that tripped me up early on is that for linear transponder birds you need to think about the doppler on BOTH the uplink and the downlink separately, they're on different bands so the shift is different in Hz. the software handles all that if you set the mode correctly in the satellite config but if you're doing it manually just be aware it's not the same correction number on both ends. caught me off guard the first few passes and i couldnt figure out why i kept missing my own downlink signal. also AO-73 has been in and out of eclipse mode lately so check its current status before planning a session around it