ok so ive been lurking on the sat ops stuff for a while and finally decided to try it this weekend. got gpredict set up, printed out a pass schedule for my area, and went outside with my ft-818 and a homemade eggbeater antenna i threw together from some online plans. the antenna is for 435/145 roughly.

the pass came overhead and i could hear... something. like there was definitely activity on the downlink around 145.950 but i couldnt make out any actual signals, just kind of a noise floor that seemed slightly elevated. i was tuning around the linear transponder passband manually and nothing really resolved into voices or cw. maybe i heard one carrier very faintly but it could have been wishful thinking honestly.

do i need to be correcting for doppler manually while tuning? im pretty sure thats the thing i was missing but i dont fully understand how to do it on the fly without having the radio hooked up to the laptop. the pass was only like 8 minutes and by the time i figured out roughly where i was on the band it was already dropping below the horizon. any advice appreciated, especially for working ao-7 or fo-29 with basic gear.

yeah the doppler thing is huge, especially on a short 8 minute pass. on fo-29 the shift across a full pass can be something like +/- 10 kHz on the uplink which sounds like a lot but you kind of get used to compensating as the bird tracks across the sky. the trick most people do when they dont have computer control is to pre-set the downlink to where you expect the center of the passband to be at your target part of the pass (usually near AOS or max elevation depending on what youre trying to do) and then just manually twitch the dial as you track. its a bit of an art form.

also the eggbeater is fine for FM birds but for linear transponders a lot of people find it undershoots on the link budget unless its built really well and has a preamp on the downlink. what are you using for the uplink side, same antenna? because if youre running like 5 watts into an omni on the uplink you might just not be getting enough into the transponder to pull your signal out of the noise on the way down. its a tight system.

so i went through the exact same thing like 6 months ago and what finally clicked for me was just listening to a busy pass first without transmitting at all. like just tune around the whole passband during a high elevation pass and see if you can hear other people working each other. if you can hear them then you know your rx chain is at least functional. if you cant hear anything on a good pass with a known active bird then somethings wrong with the setup before you even worry about the doppler stuff.

ao-7 in mode b is actually pretty forgiving once you get the hang of it but it can be tricky because that satellite is ancient and the power levels are weird depending on lighting conditions. fo-29 is more consistent imo. gpredict does have a rig control plugin that can handle doppler correction automatically if you want to set that up before your next attempt, takes maybe an hour to configure if you have a rig that supports CAT control.