ok so ive been trying to work AO-73 for the past couple weeks and im just not getting anywhere. i can hear signals on the downlink pretty clearly, like i can tell theres a passband and i can hear guys making contacts, but when i transmit i either cant hear myself in the passband at all or i just blow everything up with full quieting and everyone disappears.

my setup is a 2m yagi for uplink and a 70cm yagi for downlink on a separate radio. both antennas are handheld which is probably part of the problem but ive seen people work sats with way less so im not ready to blame the antennas yet. im running about 5 watts on uplink which i thought was reasonable.

the doppler correction is where i think im totally lost. im using gpredict to track and it shows me the doppler offsets but im honestly not sure if im supposed to be tuning the uplink, the downlink, or both. ive read like three different guides and they all seem to contradict each other on this. one says tune your uplink to compensate, another says tune downlink only, another says tune both. i dont have a fancy radio that does auto doppler so im doing it manually which is probably a mess.

any advice from people who actually do this regularly would be appreciated, been at it for two weeks and only made one contact and im pretty sure the other guy just barely heard me

the blowing everyone out of the passband thing is classic too-much-power problem. with linear transponders you really do want to run the absolute minimum you can get away with, like seriously back off until you can just barely hear yourself and thats probably about right. 5 watts on a yagi might actually be too much depending on your antenna gain and the satellite's AGC behavior. AO-73 in particular is pretty sensitive.

on the doppler question -- for a linear transponder the way i think about it is the downlink is your reference. you tune your downlink so you can hear yourself (or hear the passband clearly) and then correct the uplink to put yourself where you want to be in the passband. in practice what that means is you tune downlink for doppler all the time as it changes, and you tune uplink to find your signal. once you hear yourself, you mostly leave uplink alone unless you're drifting out of the passband, and keep chasing the downlink frequency as the bird moves. gpredict can actually drive your radio directly via hamlib if you want to try that, makes the doppler chase way less frantic during a short pass.

yeah what he said about the power level, i made the same mistake when i started. also -- are you accounting for the inverting transponder? AO-73 is inverting so if you tune UP on the uplink your signal goes DOWN on the downlink. messed me up for like a week before someone told me. means your radio needs to be in LSB on one end and USB on the other or it sounds backwards. some people just flip which mode they're in on the uplink to deal with it.