so ive been licensed for about 3 years now mostly doing HF and some local 2m stuff but i finally decided to try working the LEO birds after watching a few youtube videos and honestly i had no idea what i was getting into. picked up a used FT-847 a while back and it supposedly does full duplex which is great but the doppler correction is killing me. im using gpredict to track the pass and it shows me the doppler shifted frequencies but i cant figure out the workflow to actually keep up with it in real time, like do i just constantly twist the dial? feels like im chasing my tail the whole pass.

tried AO-73 last weekend during a decent pass, like 47 degrees elevation, and i could hear signals briefly but couldnt get any contacts. i think my uplink was way off because i could hear myself on the downlink maybe twice and then lost it. running a 7 element yagi for 70cm uplink and a 9 element for 2m downlink, both handheld which is probably part of the problem honestly.

is there a simpler mental model for how to handle the doppler or do people mostly just use rigs that have computer control for this? i feel like im missing something obvious

yeah the doppler thing clicks eventually but it takes a few passes to get the feel for it. the key thing people dont tell you upfront is that on a linear transponder bird like AO-73 you actually adjust the downlink to find yourself, not the uplink. so you park your uplink frequency somewhere reasonable and then tune the downlink until you hear your own signal, then you lock onto that and just keep tweaking as the pass goes on. the doppler shift is roughly 3.4 kHz total swing on 2m over a full pass so its not instant death, you have a little time.

gpredict can do CAT control if your FT-847 is hooked up via serial or USB adapter and then it handles the correction automatically, which is honestly the way to go once you get the cables sorted. but even without that, just knowing to chase the downlink and leave the uplink mostly alone makes a huge difference. the 47 degree pass should have been plenty workable so sounds like you were close.

handheld antennas during a 47 degree pass is a workout, im not gonna lie. i did that for probably my first 6 or 7 contacts and my arms were wrecked after. az-el rotor setup changes everything but thats a whole other rabbit hole and expense. even just getting a cheap camera tripod mount for the yagis helps a lot so you can actually focus on the radio instead of physically holding the beam.

also just something i noticed from your post -- are you sure the FT-847 is set up for full duplex satellite mode? theres a specific menu setting and it doesnt default to it, caught me out too. if its in normal mode it might be switching between TX and RX and you'd never hear yourself on the downlink while transmitting which would explain a lot