so ive been sitting on this idea for a while now and finally starting to mess around with it. basically i have 4 antennas out back — a 40m dipole, a 6m yagi, a 2m/70cm vertical and a longwire i use for 80m mostly — and im tired of going out to the shack and manually flipping the coax switches every time i want to change bands. its not even that far but in winter its a pain and i end up just not switching and running everything on one antenna which is obviously not ideal.

anyway i picked up an arduino mega off amazon a few months ago and it just been sitting in a drawer. figured i might finally have a reason to use it. my rough idea is to wire up some relays to the arduino and then have it talk to the radio somehow — either via CAT control reading the band data or just a simple button panel i build myself. the raspberry pi angle is interesting too because i could run flrig or something on a pi zero and have the band switching happen automatically when i change frequencies. not sure if thats overcomplicating it though.

has anyone actually done something like this or similar? im pretty comfortable soldering and ive done some basic arduino sketches before (mostly LED stuff lol) so im not starting from absolute zero but relay wiring and RF switching is new territory for me. main thing im worried about is RF getting into the arduino and causing weird behavior or just frying it.

yeah RF into the arduino is a real thing to watch out for, especially if your feedlines run anywhere near the control wiring. i built something pretty similar about two years ago — was using a nano at first but ended up going mega because i ran out of pins faster than expected. the relay boards you can get on amazon or aliexpress are fine for this, just make sure you get the optocoupler isolated ones, that isolation between the control side and the switched side is what saves you from a lot of headaches. i also put ferrite beads on all the signal lines going to the relay board and that cleaned things up a lot.

for the CAT control idea — totally doable. if your radio puts out band data on the ACC port or serial you can read that pretty easily. i actually went the flrig + pi route myself and its honestly not that complicated once you get flrig talking to the radio. you can write a small python script on the pi that polls flrig for the current VFO and then sends a serial command to the arduino telling it which relay to throw. latency is not an issue for antenna switching obviously.

one thing i would do differently if i started over is put proper bypass caps and maybe a small snubber circuit across the relay contacts because i had one relay chattering on me for a while and couldnt figure out why until i scoped the power rail and saw all this noise on it. just small stuff but worth doing right from the start.

dont overthink the pi side of it honestly. i tried doing the full flrig integration thing and it was more trouble than it was worth for just switching antennas. ended up just doing a simple button box with a rotary encoder and an OLED display on the arduino itself, maps to which antenna is active, does what i need. the automation angle is cool but sometimes simpler is just better and more reliable especially if you ever want to hand the shack off to someone else or you just want it to work without debugging a python script at 2am during a contest.