so i finally got around to trying some actual linear transponder work on the LEO sats after years of just doing FM birds and honestly it was more frustrating than i expected. been doing AO-91 and SO-50 for a while no problem, always wanted to try the linear ones.

got myself a copy of Gpredict set up properly, had my IC-9700 ready to go and was tracking AO-73 last thursday. the doppler correction was all over the place at first and i couldnt find my own signal in the passband at all. i knew i had to listen on the downlink while transmitting on the uplink and adjust for doppler but in practice its like... the whole thing is moving so fast and you have to tune both vfos differently because the uplink and downlink doppler shifts are in opposite directions on a linear transponder right.

eventually i heard something that might have been my CW but honestly not sure. the pass was only like 8 minutes and by the time i felt like i had a handle on what i was doing it was already going LOS. anyone have a good workflow for getting your downlink signal found quickly? feels like i was wasting half the pass just searching.

yeah the first few passes on linear birds are pretty humbling, im not gonna lie. what helped me a ton was setting up Gpredict with CAT control to actually drive the radio's tuning automatically for the doppler. once i had that working i could just focus on listening and not chase the shift manually. the 9700 plays really nice with that setup.

the trick i use for finding myself quickly is start with low power, like really low, and sweep slowly through the downlink passband before the pass while its still low elevation just to hear what the noise floor sounds like and where the transponder edges are. then when i key up i already have a rough idea of where to listen. also CW is way easier to find than SSB when you're hunting for your own signal, at least at first. the bandwidth is just narrower and it sticks out better against the transponder noise.

dont give up on AO-73 though, once it clicks it really clicks and working DX through a linear sat feels completely different from the FM ones.

the doppler on the linear birds threw me off too when i started. one thing nobody told me early on is that your receive doppler shift and your transmit doppler shift are different not just in direction but the rate changes depending on where in the pass you are. near AOS and LOS you're fighting the most shift, mid pass near max elevation its actually a bit calmer and easier to work.

i run SDR# on a separate receiver as a panadapter just watching the downlink passband the whole pass so i can see my signal visually rather than hunting by ear alone. makes a huge difference. you can actually see yourself pop up when you key down which kind of takes the mystery out of it. the 9700 has a built in scope too if you havent played with that yet, might be worth trying on a future pass.