ok so ive been licensed for about 3 years and mostly just do HF but my buddy kept telling me to try working satellites so i finally set up to give it a shot last weekend. got a couple of yagis crossed for circular polarization, hooked up to my FT-847 which supposedly does the doppler correction... or at least i thought it did automatically but i guess it doesnt really?

anyway i was trying to work AO-73 on its linear transponder and i could hear people just fine on the downlink around 145.960 but whenever i transmitted i couldnt hear my own signal come back down. i know the transponder is inverting so i was trying to account for that but honestly i kept getting confused about which direction to tune. like if someone sounds high on the downlink do i go up or down on the uplink. i feel like i spent the whole 12 minute pass just chasing my tail and never actually made a contact.

also i was using gpredict for tracking and the antenna rotators were following along pretty well but i noticed gpredict was showing a slightly different AOS time than what heavens-above predicted. only like 30 seconds off but still, is that normal? does it matter which TLE source you use?

the inverting transponder thing trips everybody up at first, dont feel bad. basically if you hear yourself too high on the downlink you need to tune your uplink frequency DOWN, not up. its counterintuitive because your instinct is to chase the signal in the same direction but with an inverting transponder it works backwards. once that clicks in your head it becomes second nature.

for the doppler the 847 will do split doppler correction if you set it up right in gpredict under the radio control settings, you need to tell it which VFO is uplink and which is down and it handles the compensation on both sides. if you just had it correcting one side thats probably why you were losing yourself. took me a while to figure that out too, the gpredict documentation isnt super clear about it.

on the TLE thing yeah 30 seconds difference between sources is pretty common, depends on how fresh the elements are and which source they pulled from. spacetrack.org is usually the most current, i update mine every few days when im planning a session. for a low bird 30 seconds can mean the difference between having the rotators pointed at the right spot or staring at empty sky at AOS so its worth keeping them fresh.

yeah gpredict with fresh TLEs from celestrak has been more accurate for me than heavens-above, i think heavens above caches their elements longer or something. anyway welcome to satellite, its addictive once you actually make a contact. AO-73 can be pretty crowded on weekends so sometimes its hard to find your own downlink signal with everyone piling on