so ive been chasing LEO passes for a couple months now mostly on FM birds like SO-50 and that went fine once i figured out the timing. decided to try AO-73 last week since everybody says the linear transponder is where the real fun is and honestly i kind of wish i hadnt because now im obsessed and also confused.

the doppler thing is killing me. i get the concept, uplink and downlink shift in opposite directions on the inverting transponder so you have to chase them in opposite directions. but in practice my brain just cant keep up. i was using Gpredict and had it set to compensate but i think i had the wrong TLE or something because my signal kept drifting off and i could hear other guys just fine holding their freqs steady.

also not sure if my downlink audio was just weak or if i was off passband. running an FT-817 and a handheld yagi which i know isnt ideal but i figured id try before spending money on a proper az/el setup. anyone been through this learning curve and have tips that actually helped it click

yeah the doppler on a linear bird trips everyone up at first. the inverting transponder thing means when you tune your uplink up your received signal comes down in frequency, so most people just learn to ignore the uplink rx and focus entirely on locking the downlink first. find your own signal on the downlink and once youve got it, just keep tuning the downlink to hold it in place and let the rig handle the rest or manually chase it. dont touch the uplink once youre in the passband unless you actually want to qsy.

the 817 and handheld yagi is actually a pretty decent starting combo, ive worked AO-73 with less. make sure your TLEs are fresh, like within a few days fresh, old elements will throw off the doppler prediction enough to make you think somethings broken when its not. Gpredict should handle the compensation if you have the right satellite selected and the right RX/TX offsets configured for the passband edges. check the amsat frequencies page for the current transponder passband, it moves sometimes after they do reconfigs.

honestly same boat here not long ago. what helped me was just doing a few passes where I wasnt even trying to make contacts, just listening to the downlink and watching the waterfall in SDR# or whatever to see how the doppler actually looked visually. once you see the curve on a waterfall it kind of makes sense in a way that reading about it doesnt. after that the manual tuning felt way less chaotic.

also AO-73 has pretty decent passband strength when the bird is high elevation so if youre really struggling to hear anything on a good pass it might be your yagi pointing, those handheld ones are way more directional than people expect and you lose signal fast if youre even a little off especially near the horizon.