so ive been trying to work AO-73 for a few weeks now and i keep hearing my own downlink but nobody responds and i cant figure out if its my doppler correction thats off or if im just not loud enough on the uplink. running about 5w into a handheld yagi on the 435 uplink and listening on 145 with a separate whip which is probably the problem honestly.

the thing that confuses me is the linear transponder is inverting right, so when i tune up on the uplink my signal goes down on the downlink. i get that part. but im using gpredict to track and sometimes the footprint shows me well within range but i still cant hear anything on the downlink at all — not even the beacon. wondering if the satellite is maybe in eclipse or something or if my timing is just off. passes here are short, maybe 8-9 minutes on a good one at maybe 30 degrees max elevation which doesnt help.

anyone worked this bird with a modest setup and had luck, or is this one of those satellites where you really need proper crossed yagis to get anywhere

the whip on the downlink is almost certainly killing you. 145 downlink from a LEO is weak enough that even a small yagi makes a huge difference — going from a whip to even a 5 element yagi is probably 8-10dB and thats the difference between hearing nothing and copying signals fine. i worked AO-73 for a while with a single yagi on each band and it was totally workable on good passes, you dont need crossed yagis to have fun on it but you do need gain on both ends.

also worth checking your gpredict keps are fresh — if theyre more than a few days old on a low bird the timing can be off enough that you miss the pass window or the doppler corrections are wrong. i usually grab fresh keps from celestrak the morning of an operating session. the inverting transponder thing you described sounds like you have that figured out correctly so probably not the issue there.

yeah 30 degree max passes are rough, i wouldnt even bother with those personally and wait for something higher. also are you correcting doppler on both uplink and downlink simultaneously? because if youre only chasing it on one side the math gets weird with an inverting transponder. gpredict can drive the rig directly if youre using something with CAT control and that helps a lot once you get it set up, manually tuning is kind of a nightmare especially on short passes