so ive been chasing LEO sats for about 3 months now and i finally made a couple contacts through AO-73 last week which was pretty exciting. been using a Arrow antenna and an FT-818 for uplink, FT-736R for downlink. the problem is my doppler correction is all over the place. im doing it manually which i know is the wrong way to go about it but gpredict keeps crashing on me before i can get the rig control stuff sorted out.

the linear transponder on AO-73 is inverting which i understood beforehand, so i know when i tune up on the uplink the signal goes down on the downlink, but theres this like 3-4 second window around TCA where everything just goes sideways and i lose my own signal completely. is that normal or am i doing something wrong with the antenna transition? im using a single crossed yagi at the moment and flipping polarization manually which is probably contributing to the chaos.

also do people actually track by hand that successfully or does everyone just use SDR and let software handle it, because the guys at my club act like its super easy to do it manually but i dont know man it feels pretty hectic on a 10 minute pass

the doppler thing around TCA is pretty normal honestly, especially if youre doing it by hand. the rate of change is fastest right at closest approach so thats when you'd need to be cranking the dial the quickest. most people find it easier to just slow down a bit and accept you might lose yourself for 20-30 seconds in that window, its not the end of the world.

gpredict crashing -- what OS are you running? ive had issues with it on certain ubuntu versions and the fix was just pulling a slightly older build. the rig control stuff through hamlib can be finicky too depending on how your serial port is set up. once you do get it working though its a total game changer for the linear birds, especially on something like AO-7 where the pass geometry is all over the place depending on the mode.

the crossed yagi polarization flip is definitely adding to your workload. some guys just park it at 45 degrees and eat the loss rather than fuss with it during a fast pass. works fine for anything not too deep in the noise.

yeah manual doppler on a linear transponder is uh... a lot. i tried it for like two weeks before i finally got gpredict talking to my radio and honestly the difference is night and day. the inverting transponder makes it feel even more chaotic because your instincts are wrong until you build new ones basically.

one thing that helped me before i got the software working was printing out a doppler table for the specific pass from heavens-above or gpredict beforehand and just working off that. its not perfect but at least you have a rough schedule of how much to shift and when instead of guessing in real time.