so i've been listening to LEO passes for a while now just with an arrow antenna and an old ft-817 but i finally tried actually working through AO-73 last weekend and wow that was a different experience than i expected. managed to get a few contacts but i feel like im doing something fundamentally wrong with the doppler correction stuff

what i was doing was manually tuning to compensate as the pass went on but keeping my uplink fixed and adjusting the downlink — is that right? i read somewhere you're supposed to do it the other way around or maybe both? honestly it got confusing fast and by the time i thought i had it sorted out the pass was already going below the horizon. also the signal inversion thing caught me off guard, i knew about it in theory but forgot in the moment and was trying to tune the wrong direction for a bit

im using gpredict for tracking on the laptop which is great but i havent figured out how to get it talking to the radio automatically yet. anyone running rigctl or hamlib with an 817 that actually works reliably? the docs for that stuff feel like theyre written for people who already know how to do it

yeah the doppler thing trips everybody up the first few times, dont feel bad. for linear transponders the way i think about it is — keep your downlink VFO tuned so you can hear yourself (or find the passband), and let your uplink drift or correct that manually. the reason is you want to hear what you sound like on the satellite so you can tell if youre even in the passband. once you hear yourself then you compensate. if you fix your uplink and just chase with the downlink you might never even know if your signal is getting through.

the signal inversion thing on AO-73 means if you tune up on the uplink your signal goes down on the downlink, so yeah that definitely bites people. just burns into your brain after a few passes.

for rigctl and the 817 i honestly just gave up and do it by hand. the cat control on the 817 is kind of flaky and i found the latency made gpredict corrections feel weird anyway. some people swear by it but for a 10 minute pass i'd rather just tune.

gpredict with hamlib and the 817 — i got this working but it took an afternoon. you need the right baud rate set on the radio (4800 i think, or maybe 9600, check what your radio menu says) and then in gpredict under interfaces you set up a radio with the correct port and make sure youre running rigctld as a daemon first before gpredict tries to connect. the ordering matters for some reason.

honestly though even when it works the doppler correction only updates every few seconds and for SSB it can sound a little steppy. works fine for the low passes where doppler isnt moving as fast, less great right at AOS when the rate is highest. FO-29 was the one i really noticed it on, AO-73 might be a bit more forgiving i cant remember the exact transponder bandwidth offhand.