so ive been wanting to get into satellite operation for a while now and finally pulled the trigger on setting up a basic station for LEO work. running a yaesu ft-991a into a pair of crossed yagis i built from a design i found online, elevation rotor is a cheap but functional gs-232 compatible unit i grabbed used, az rotor is an old prop pitch thing that works well enough.

been using gpredict for tracking and it seems fine, i can get the doppler correction working through hamlib to the rig which is cool. my issue is im not really sure im understanding how the linear transponders work in practice. like i get the theory - you transmit on the uplink frequency and listen on the downlink - but when im actually on something like FO-29 or AO-73 i feel like im constantly chasing my own signal around and everyone else sounds like theyre underwater or just totally garbled.

is that just the reality of working through a linear sat or am i missing something fundamental here. ive read that you have to manually compensate for doppler on linear birds because the software only corrects one side? not sure if thats my problem or if my antennas are just not performing. az/el angles look right in gpredict at least.

yeah the doppler thing on linear transponders catches everyone at first. gpredict (and most software) will correct your downlink frequency automatically but you have to manually tune your uplink to compensate as the pass progresses - or at least thats how most people set it up. what you really want to do is tune your uplink until YOU sound clear to yourself on the downlink, not try to hit a fixed frequency. the sat doesnt care what uplink freq you use within the passband, it just translates the whole chunk up or down. so lock your receiver on a clear spot and adjust transmit until your signal comes back sounding right, then talk to people from there.

also FO-29 has been having some power issues lately and the transponder is only on part of the time, might want to check the amsat status pages before assuming its your setup. AO-73 should be more reliable for practicing this stuff.

the "underwater" sound is probably your antennas honestly. crossed yagis need the phasing to be right for circular polarization and if thats off even a little you'll get really inconsistent signals, especially as the sat moves through different parts of the sky. i chased my tail for weeks thinking it was my doppler correction before i figured out i had one of my phasing cables cut to the wrong length. worth double checking. what design did you use for the yagis?