so i finally dragged myself out to the backyard last weekend with my FT-817 and a pair of arrow antennas and actually made some contacts through AO-73. been wanting to do this for probably two years and just never got around to it. overall it went better than i expected but i have some stuff i cant quite figure out.

the doppler correction is what's killing me. im doing it manually which i know is kind of painful but i dont have a rotator setup yet so im just hand holding the antennas anyway. i was using gpredict on my laptop to track the pass and calling out frequencies to myself like an idiot but i kept losing my own downlink signal partway through the pass because i wasnt compensating fast enough on the uplink side. like i'd find myself, then work the doppler on the downlink a bit and then suddenly my uplink is wrong and i've drifted somewhere else in the passband.

also -- the inverting transponder thing. i knew about it going in but i still keep getting confused in the moment whether to tune up or down. is there a trick people use to keep this straight in their heads while also trying to track the bird and hold the antenna and watch gpredict? feels like a 4 handed operation sometimes. any tips from people who've been doing this a while would be great.

yeah the inverting transponder thing tripped me up for a long time too. the way i think about it now is -- if your signal sounds too high pitched in the passband, tune your TX frequency DOWN, not up. opposite of what feels natural. after a few passes it becomes muscle memory but until then it's genuinely confusing especially when you're also juggling the antenna and trying not to fall over a lawn chair.

for doppler on a linear bird like AO-73 what i eventually started doing is locking the downlink and only correcting the uplink. gpredict actually has a mode where it handles this -- if you have it connected to your radio via CAT it'll move the RX to keep your signal in the passband. but if you're manual like you are right now, just try to get in the habit of moving the TX in bigger steps less frequently rather than chasing it constantly. the passband is wide enough that you have some breathing room, you dont need to correct every 30 seconds at mid-pass.

also AO-73 specifically goes linear only when its in eclipse i think? worth double checking the current mode status on amsat's site before a pass because sometimes its FM and you'll be sitting there confused why your SSB isnt doing anything.

hand holding the arrow for a full pass is honestly a workout especially if its a high elevation one. i did it for about 6 months before i caved and built a cheap az-el mount out of two TV rotators. not perfect but gpredict drives it and i can actually focus on the radio part now instead of trying to be the antenna.

one thing that helped me early on was doing a few passes just listening, not transmitting at all. just tune around the passband and hear where other people are and how the doppler moves everything over the course of the pass. gives you a feel for how fast things shift at different elevations. LEO passes are fast and the doppler curve is steepest at AOS and LOS, middle of the pass is actually pretty calm. so if you're just starting out maybe make your contacts near max elevation and give yourself a break.