so ive been messing around with FO-29 and AO-73 for a few weeks now and the doppler correction is just killing me. im using SDR# with a plugin for doppler on the receive side but my uplink is just a handheld pointed at a yagi which i know isnt ideal but bear with me here. the problem is even when i think im tuned right i can hear myself come back through the transponder way off from where i expect, like sometimes i find myself and then i lose it again before i can even say my callsign properly.

i tried using gpredict for the tracking data and its pretty decent but syncing the doppler correction to my actual radio while also manually adjusting the uplink is just a lot to juggle. is there a way people usually handle this that isnt a full computerized rig with CAT control? i dont have CAT on my HT obviously lol. also is there a trick to just parking somewhere in the passband and staying put rather than constantly chasing the frequency? i feel like ive seen people mention this somewhere but cant remember where.

the passes where the max elevation is under like 20 degrees are basically useless for me right now, i think my antenna situation is part of that but still. any tips appreciated, been lurking here for ages and figured id finally just ask.

yeah the dual doppler thing on linear birds is the classic headache when youre starting out. the trick a lot of people use is to just pick a spot in the passband and then instead of correcting your uplink, you correct your downlink to follow yourself. basically you tune until you hear your own signal on the downlink and you keep that frequency locked in your head or just leave the RX tuned there and chase it. your uplink freq will drift as seen from the sat but if you compensate on receive you can at least hear yourself which is the important part for making contacts.

gpredict with CAT control really is the way to go long term, even if your HT cant do it you might want to run a separate receiver that can be controlled. a lot of guys use an FT-817 or similar for sat work specifically because of the CAT. the HT uplink situation is workable for low passes but youre gonna have a bad time on anything under 25 degrees honestly, its just not enough link budget especially on the uplink side.

also make sure your TLE data is fresh, gpredict can pull from celestrak and if your TLEs are more than a few days old on an LEO the pass predictions will be off enough to matter.

i had almost the exact same frustration with AO-73 a while back. what finally clicked for me was just accepting that the first minute of a decent pass is basically practice and the middle 3-4 minutes is where you actually try to work someone. dont stress about the low elevation stuff, everybody struggles there.

one thing i dont see mentioned much is that on the linear transponders the inverting passband means your doppler correction is kinda counterintuitive at first. USB on downlink, LSB on uplink for most of these birds, and when the sat is coming toward you the downlink actually goes up in freq while your uplink needs to go down. took me way too long to internalize that and i kept correcting the wrong direction for like two weeks straight.