so ive been licensed for about 3 years now mostly doing HF and some 2m FM stuff locally but lately ive been really curious about working through the linear transponder satellites like AO-7 and the Fox sats. watched a few youtube videos and it seems doable but also kind of intimidating because youre basically chasing a moving target while also dealing with doppler shift and trying not to stomp on everyone else on the passband at the same time.

my current setup is a dual band yagi i built from a design i found online, feeding a FT-818 which i know isnt ideal but its what i have. from what i understand i need to be able to split the tx and rx to different bands - uplink on 70cm and downlink on 2m for most of the FM birds but the linear ones are different right? like AO-7 is 2m up and 10m down in one mode? or am i misremembering that.

also whats everyone using for tracking software these days. i tried gpredict and it seems solid but the doppler correction stuff with my radio is a little confusing to set up. does it actually auto-correct the frequency in real time or do i have to babysit it the whole pass. any pointers appreciated, this whole thing seems like a rabbit hole i want to fall into

yeah gpredict is the way to go honestly, its what most people use and once you get the rig control sorted through hamlib it does do real time doppler correction, you just have to make sure your radio is set up as a rig in hamlib and gpredict knows which VFO to tune. theres a bit of setup pain the first time but after that it mostly just works. i had issues with it for a while because i was running an older version that had a bug with certain rigs but updating fixed it.

on AO-7 - youre partially right. Mode A is 2m uplink and 10m downlink, Mode B is flipped, 70cm up and 2m down. the thing about AO-7 is its been running since 1974 and the batteries are dead so it only works when its in sunlight. its actually kind of amazing it still works at all. Mode B is way more popular because most people dont have a 10m receive setup ready to go at a moments notice while also pointing a yagi at a moving satellite.

FT-818 is fine for starting out, plenty of people have worked linear sats with worse. the bigger thing is your antenna azimuth and elevation capability - if youre just doing azimuth only youll miss passes where the bird goes high and crosses overhead. still workable but youll have gaps. whats your antenna mount situation like

i just started doing this like 6 months ago and honestly the first few passes i got nothing because i was confused about the inverted passband thing on linear transponders. basically if you tune your uplink higher, your signal appears lower on the downlink - so you have to think kind of backwards when youre trying to find your own signal. took me an embarrassingly long time to figure that out from just reading, had to actually try it and fail a bunch before it clicked.

one thing that helped me a lot was just listening first without transmitting. spend a whole pass just finding where signals are on the downlink and getting used to how fast the doppler is actually moving. its faster than you expect near AOS and LOS and almost nothing in the middle of a good overhead pass. once you can hear other people working each other you start to get a feel for it. then try transmitting and finding yourself on the downlink before you call CQ or anything.

also get your TLE files updated regularly, gpredict has a way to download fresh ones but if theyre old your timing will be off and youll be pointing the wrong direction especially for low passes near the horizon