so ive been messing around with this for a few weeks now and im starting to think i may have bit off more than i can chew. basically i have an old hygain rotator that still works fine mechanically but the controller is pretty much toast, one of the caps popped and i traced a couple burnt traces but at some point i just figured why not build something with an arduino instead of trying to resurrect a 40 year old controller board.

my plan is to use a nano with an L298N motor driver and read the azimuth pot with the analog input, then display the heading on a little oled screen. pretty straightforward on paper. the problem im running into is the pot in the rotator is super nonlinear, like i get decent readings from maybe 90 to 270 degrees but the ends of the range are just mushy and inconsistent. not sure if thats a bad pot or if i need to do more calibration in software or what.

also thinking about tying this into a raspberry pi at some point so i can drive it from hamlib or maybe wsjtx automatically during contests but thats a whole other rabbit hole. anyone gone down this road before, curious what you ran into.

yeah ive done almost exactly this with a yaesu g-450a. the nonlinear pot thing is almost certainly just wear on the resistive track, they get dead spots especially at the ends where it parks most of the time. what i did was just map it in software — take like 20 readings across the full rotation and build a lookup table in the arduino sketch, then interpolate between points. its not elegant but it works and you only have to calibrate it once. the analogRead values dont have to be linear as long as you know what they correspond to.

the L298N should be fine for the motor drive but watch your current draw on startup, those old rotators can pull a decent spike and the 298N gets warm fast if youre not giving it adequate heatsinking. i fried one before i figured that out.

for the hamlib integration on the pi side, rotctld is your friend. there are some sketches floating around on github that implement a serial protocol compatible with rotctld so wsjtx or any other hamlib aware program can just talk to the arduino directly over usb. saves you from needing the pi in the middle if you dont want it there.

the pot is probably just worn out, those things dont last forever especially if the rotator sat outside for years. replacement pots arent too expensive, just make sure you match the resistance value and the shaft diameter. might be worth swapping it before you spend too much time fighting the software side.

i went a slightly different direction and used a raspberry pi zero W as the main controller with a small motor hat, mostly because i wanted wifi and didnt want to deal with usb serial from a separate machine. runs flightaware style but for the antenna basically. not saying its the better way just what made sense for my setup.