so ive been licensed for about 3 years now and mostly do HF but a buddy of mine got me interested in working the LEOs, specifically AO-73 and FO-29. i set up gpredict on my laptop and thats going okay, it tracks the passes and i can see the doppler shift displayed but here's where i get confused -- do i actually have to manually retune constantly while the satellite is overhead or is there some way to automate this? i have an IC-9700 which i think can do CAT control but ive never messed with that stuff before.

also on FO-29 which has a linear transponder, i keep reading that you have to invert your tuning direction on SSB which makes zero sense to me. like if i tune up on my uplink i have to tune down on the downlink? i tried working a pass yesterday and just could not figure out what i was hearing, felt like i was chasing signals all over the place and never actually made a contact. the pass was like 7 minutes and it went by so fast i didnt even have time to think.

any tips for someone starting out with this? i have a decent arrow antenna and a handheld for now but might upgrade later if i get into it more.

yeah the inverting thing trips everyone up at first. basically on a linear transponder the passband is inverted, so if a station moves up in frequency on the uplink you'll hear them move down on the downlink. it's just how the transponder mixes it. once you get used to it it becomes second nature but for the first few passes it's genuinely disorienting.

for the doppler -- yes you really do have to retune constantly, that's just the reality of LEO work. the shift on FO-29 is something like plus or minus 10 kHz over a whole pass which sounds small but it moves fast near AOS and LOS. gpredict can actually send CAT commands to the 9700 and handle the doppler correction automatically for both uplink and downlink, you just have to set it up under the radio interfaces menu. there's a pretty decent guide on the AMSAT website for doing this with icom rigs. once you get that working it makes a huge difference, you can actually focus on operating instead of just spinning the dial.

the arrow antenna is fine to start, honestly. i worked my first 30-40 contacts with an arrow and an FT-817 so dont let anyone tell you need a big az-el setup to get started.

FO-29 has been having some power issues lately so the transponder isnt always on during every pass, worth checking the AMSAT status page before you plan a session around it. AO-73 is generally more reliable lately from what ive seen.

and yeah 7 minutes sounds like a lot until youre actually standing there trying to hold an arrow antenna and tune a radio at the same time lol. i still mess up passes i've been doing this like two years. the CAT control setup is worth the afternoon it takes to figure out, total game changer.