so i've been wanting to get into LEO satellite operation for probably two years now and last weekend i finally just did it. setup is nothing fancy, just a FT-818 for the uplink on 70cm and an old IC-821H i borrowed from a club member for the downlink on 2m, running into a pair of hand-aimed arrow antennas. tracking with gpredict which i've been messing with for a few weeks getting the pass predictions dialed in.

AO-73 was my target because i kept reading it was good for beginners and the linear transponder makes more sense to me than FM birds since i'm mostly an HF SSB guy. pass was about 8 minutes from my location, elevation peaked around 34 degrees which i figured was pretty decent. i could hear the downlink clearly once it got above maybe 12 degrees, heard a couple stations working each other which was cool.

here's where it got weird though — i could never quite find my own uplink signal on the downlink. i know you have to account for doppler and the inverting transponder means you tune opposite directions on tx vs rx, i had read all that. but in practice i was completely lost trying to chase it in real time. gpredict was handling the rig doppler correction through hamlib but i dont think it was actually talking to both radios correctly, maybe just one of them. ended up just listening the whole pass which was still fun but frustrating.

is there a trick to initially finding your own signal on a linear bird? do most people set up some kind of split tracking or just manually tune until they hear themselves? feels like im missing something obvious.

yeah the inverting transponder thing trips everyone up the first few times, dont feel bad. the doppler correction in gpredict through hamlib can be finicky depending on how you have the rig control configured — if its only correcting one radio youre going to drift off fast especially near AOS and LOS where the doppler rate is highest.

what i do, and this isnt the elegant solution but it works, is start a pass by putting out a quick carrier on the uplink near the middle of the transponder passband and then sweep the downlink receiver maybe 5-10 kHz above and below where gpredict says you should be. once you hear yourself lock onto that and then let gpredict take over from there. the key is getting that initial acquisition done early in the pass while the doppler rate is slower. once youre over 20 degrees elevation and the satellite is closing fast the rate really picks up and chasing it manually is a nightmare.

also check that hamlib is actually addressing both radios with the right COM ports, sounds like maybe it wasnt. AO-73 is a great bird to learn on, the linear transponder is low power but its definitely workable with your setup.

I had the exact same problem when I started. One thing that helped me was just completely ignoring the TX doppler correction at first and manually tuning the uplink by ear after I locked the downlink. Sounds backwards but it kind of clicked faster that way. The inverting part means if you go up on TX you go down in the passband on the downlink so once you internalize that it becomes more intuitive than trying to think about it mathematically in the middle of a pass.

34 degree max elevation is pretty solid for a first attempt honestly, that's plenty of time if you can get the workflow sorted. I'd also say try FO-29 if you get a chance, seems to have a bit more activity on weekends at least from what I've seen.