so i finally got around to actually trying a LEO pass last weekend instead of just reading about it for the past year. been using gpredict for tracking and i have to say once i got the doppler correction set up properly it actually works pretty well, at least for the tuning side of things.

the pass i was watching was AO-73 and i could hear signals on the downlink no problem - 2m receiver, yagi pointed roughly in the right direction by hand. but actually making a contact is a whole other thing. my question is about the linear transponder specifically - i understand you need to compensate for doppler on both uplink and downlink independently and that gpredict can do this automatically if you have rig control set up, but i only have one radio right now (FT-817) and ive been trying to wrap my head around how people do this with a single rig.

is it even practical to do full duplex on one radio or do i just need to accept that ill need two rigs eventually? i know some people do it with a handheld for downlink monitoring but im not sure how well that works in practice when youre also trying to tune and manage an antenna at the same time. feels like youre basically juggling three things at once during a 10 minute pass.

yeah honestly doing LEO linear with a single radio is kinda painful. you CAN do it - a lot of people start that way - but you end up essentially flying blind on the downlink while youre transmitting which means you have no way to know if youre actually in the transponder passband or drifting all over the place stepping on other contacts. the classic beginner mistake is transmitting too much power too because you cant hear yourself and assume more is better. drives the other station operators nuts.

the handheld for downlink monitoring actually works better than youd think as long as the sat is above like 20 degrees elevation, you dont need much antenna for the downlink receive. a lot of guys use an SDR dongle as a dedicated downlink receiver now, cheap and you can see the whole passband at once in the waterfall which makes finding your own signal way easier. gpredict with CAT control on the 817 for uplink doppler and just manually tune the SDR - its a bit of a workflow but it gets the job done without a second full radio.

im kind of in the same boat, been at this maybe 3 months. one thing that helped me a lot was doing a few passes just listening only, no transmitting at all, just to get a feel for how fast the doppler shifts and how the signals sound through the transponder. AO-73 in particular the passband isnt huge so its pretty easy to hear if someone is doing something wrong lol.

also gpredict is great but make sure your TLE files are recent, like within a week or so ideally for the lower LEO birds. i was getting confused why my tracking felt slightly off and turned out my TLEs were like 3 weeks old which for a 400-something km orbit makes a noticeable difference in predicted AOS and the azimuth/elevation curves.