so i finally got around to trying satellite work after years of telling myself id get to it eventually. started with AO-91 since everyone says thats the easiest entry point and yeah, managed to hear myself in the downlink which was pretty satisfying honestly. using a arrow antenna handheld with two HTs and full duplex which was a pain to set up but worked.

heres where i got lost though - i want to try SO-50 still but more importantly i keep reading about FO-29 and AO-73 and the linear transponders on those. i sort of understand the concept, SSB and CW passband transponder, your uplink gets inverted on the downlink... but when people talk about doppler correction on a linear transponder it seems way more involved than just having presets for the FM birds. like do i need to be constantly tuning during the pass or is there software handling all that. im using SDR# for receive on a rtlsdr v3 with the nooelec lna, uplink is on a vx-8gr for now.

also what are people using for tracking software these days, i was on heavens-above for a while but someone mentioned gpredict and i havent tried it yet. does it actually do the rig control for doppler compensation automatically or is that a separate thing you have to configure

gpredict absolutely does rig control for doppler, thats kind of its main thing for satellite work. you set it up through hamlib and point it at your radio, and it'll tune both your uplink and downlink frequencies in real time as the bird moves. for the linear transponders thats pretty much essential because you cant manually crank the dial fast enough to keep up, especially near AOS and LOS when doppler shift is changing quickest.

the inversion thing trips everyone up at first. on a linear inverting transponder if you tune your uplink higher your downlink goes lower. so if you find your signal on the downlink and the QRM is moving up you tune your uplink down to chase it back. becomes second nature after a couple passes but yeah its weird the first few times. FO-29 has been kind of intermittent lately so id maybe start on AO-73 if its in sunlight during your passes. check amsat's status page before planning anything.

your SDR setup should be fine for receive, the nooelec lna is decent enough for 70cm downlinks if you dont have a preamp issue. main thing is making sure your frequency reference is stable enough, cheap dongles can drift and on SSB even small drift is noticeable

yeah gpredict is what basically everyone uses now, heavens-above is fine for just looking up pass times but its not gonna do anything for you in terms of rig control. the hamlib integration is a bit fiddly to get working the first time depending on your OS but once its dialed in it just works.

one thing i'd add - when youre on a linear transponder bird try to find an empty spot in the passband and call CQ there rather than just spinning around looking for signals. the passband isnt that wide and everyone piling on top of each other is a problem. also run the lowest power you can get away with, some guys show up with amps and just stomp all over the transponder and it degrades for everyone. bit of a soapbox thing for me lol but it matters more on linear birds than FM.