so ive been trying to work AO-73 for about three weeks now and i can hear the downlink fine on 145.935 but i cannot for the life of me find my own signal coming back down. running about 5 watts into a small yagi i built from a tape measure design, elevation is maybe 20-30 degrees on most passes i've been trying. full duplex capable with two HTs and a laptop running gpredict for doppler tracking.

what i think is happening is im not compensating for doppler properly on the uplink side — im adjusting the downlink as i go but i set the uplink and kind of leave it. someone told me the linear transponder inverts the sideband so if i go up in frequency on uplink my signal actually comes down in frequency on the downlink? i think i have that backwards or maybe i have the whole thing backwards. also not sure if 5 watts is just too little for that bird.

gpredict is showing good acquisition of signal times and the passes look decent overhead, northeast US if that matters. anyone worked this one recently and can tell me if there's something obvious im missing

yeah the inverting transponder thing is exactly what's biting you i bet. AO-73 has an inverting linear transponder so when you tune UP on the uplink the signal comes DOWN on the downlink passband — so you have to tune them opposite directions to track doppler. a lot of guys set up their rigs so one VFO controls both and handles the inversion automatically but if you're doing it manually you really have to think backwards and it's confusing at first.

5 watts should be enough honestly, ive worked it with less into a handheld yagi, the key is the antenna pointing more than power. at 20 degrees elevation your path loss is higher and the yagi needs to be pretty well aimed. whats your beamwidth on that tape measure antenna, those can be pretty narrow. also are you in SSB mode on both ends? people sometimes forget and leave one end in FM which obviously wont work on a linear transponder.

this was me like six months ago lol. the doppler thing with inverting transponders broke my brain for a while. what finally clicked for me was just working it live with someone on the ground who could tell me they heard me — joined a local club that does satellite nets and someone spotted my signal on a webSDR and told me to tune up and i could hear myself move down, then it just made sense. gpredict has a doppler correction mode that can output to some radios via CAT and handle the inversion for you, worth looking into if your rig supports it. IC-9700 does it natively which is kinda cheating but also amazing.