so i've been wanting to get into LEO satellite work for a while now and last weekend i finally just went out and did it with a cheap arrow antenna and my ft-818. got a few contacts on AO-73 which was honestly way more exciting than i expected, hearing your own signal come back through the bird is kind of surreal if you've never done it before.

anyway my main issue is keeping up with the doppler shift on both the uplink and downlink simultaneously. i was using gpredict on my laptop but its kind of a pain to be adjusting both radios at the same time while also trying to hold the antenna and talk. i've seen some people mention just tracking the downlink and leaving the uplink fixed or doing it in reverse, not sure which is the more accepted approach. also does anyone actually use the doppler tuning automation in gpredict connected to the radio via CAT or is that more trouble than it is worth for a single pass?

im running full duplex btw with the 818 on uplink and an sdr on the downlink side so i can hear myself, that part works pretty well actually.

yeah the two-radio doppler thing is a real juggling act at first. what most people settle into is tracking the downlink and just nudging the uplink occasionally, because the passband on a linear transponder is wide enough that small uplink errors mostly just move you around in the passband rather than losing you entirely. the doppler rate on something like AO-73 at low elevation is manageable if you do it every 20-30 seconds or so rather than constantly chasing it.

i do use gpredict with CAT on my IC-9700 and once its set up properly it does help a lot, but the initial configuration is genuinely annoying especially if your radio needs specific polling rates. worth doing if you're going to be doing this regularly though. the bigger thing nobody tells beginners is that your antenna pointing matters way more than perfect doppler correction. ive lost passes because i was fiddling with freq instead of keeping the beam on the bird.

congrats on the first contacts, AO-73 is a great starter bird. i'm pretty new to this too and went through the same doppler confusion a few months back. honestly what helped me was just doing a few passes as receive only first to get the feel for how fast the shift actually is before trying to work anyone. its not as dramatic as i thought it would be, you have a few seconds at least before it becomes a problem.

one thing i do now is pre-program the start and end frequencies into memory channels and just step through them roughly during the pass instead of trying to tune smoothly. its janky but it kind of works lol. definitely want to try the gpredict CAT thing eventually but havent gotten there yet.