so ive been chasing the idea of working satellites for a while now and finally got around to setting up for it. got a funcube dongle plus for downlink monitoring and im using my ft-991a for the uplink side. antenna is just a cheap arrow yagi that i'm hand-holding for now which honestly works better than i expected.

the problem im running into is the doppler correction thing. i get the concept - the satellite is moving so the frequency shifts - but when i try to manually tune during a pass i feel like im always chasing my tail. by the time i find where i think my signal is the bird has moved and everything shifted again. and thats assuming i even found my own signal in the first place which on the linear transponders is way harder than i thought vs the FM birds.

im using gpredict for tracking and it does have doppler correction built in but i havent figured out how to get it talking to the 991 properly via CAT. anyone else gone through this setup or have tips for getting the CAT control working so gpredict can just handle the tuning automatically? feel like that would fix most of my frustration here

yeah the linear transponders are a completely different animal compared to just hitting AO-91 or whatever on FM. took me a while to get my head around it too. the thing people dont always explain clearly is that on a linear bird you need to correct doppler on BOTH uplink and downlink, and they shift in opposite directions relative to each other which makes it extra confusing when youre tuning manually.

for gpredict and the 991a - i got that combo working a while back. you need to enable CAT in the 991a menu, set baud rate to 38400, and in gpredict go to edit > preferences > interfaces and add a new radio. set it to hamlib, FT-991 (not 991A specifically, just use the 991 entry, works fine), and point it at whatever COM port your USB cable shows up on. then when you open the doppler control window in gpredict you can hit track and it'll drive the rig. theres a slight quirk where if you have the 991 in split mode gpredict can get confused so i just let gpredict handle all the VFO switching itself.

hand tracking with the arrow is totally doable for lower passes but anything above like 30 degrees elevation and youre spinning around trying to keep it pointed and tune at the same time. eventually you want even a cheap az/el rotor setup but i worked plenty of contacts with the arrow before i got there

im kinda in the same boat actually, been lurking on this because i just started messing with FO-29 and the doppler on that thing is wild compared to the FM sats. one thing that helped me was to just pick a known strong beacon or someone elses signal on the downlink passband first and use that as a reference to understand how fast things are shifting before i tried to transmit anything. kind of like getting your bearings before jumping in.

also gpredict is great but make sure your TLE data is actually fresh - ive been burned before where i had stale elements and the pass predictions were off by enough to cause problems especially for short low elevation passes