so ive been messing around with this idea for a few weeks now and finally got something half working. basically i have a hex beam and a vertical out back and im tired of running out to the shack every time i want to switch between them for different bands. figured an arduino with a relay board could handle the switching logic and maybe tie into my radio's band data output.

got a uno sitting on the bench that wasnt doing anything and wired up one of those 4 channel relay modules from amazon, the blue ones. logic is pretty simple, just reading the BCD band data off the accessory port and then firing the right relay. problem is im getting some weird RF getting into the arduino when i transmit, like it just resets or goes haywire on 40m especially. shielding the whole thing didnt seem to fully fix it. anybody dealt with this before or have a better way to isolate the control lines from the RF environment in the shack

also been thinking about whether a raspberry pi would be better for something like this since i could tie it into logging software too but honestly the arduino feels right for something this simple, dont need a whole linux box just to flip a relay

yeah the RF getting into the arduino is super common with these setups, had the exact same thing happen with a band decoder i built last year. the relay modules usually have optoisolators but the input lines to the arduino itself are wide open and basically act like little antennas. what helped me was putting ferrite beads on every wire going into the thing, like literally every single one including the power leads, and then adding a 100nf cap to ground right at each input pin. also make sure your ground braid is actually a proper RF ground and not just a long wire because that can make things worse actually.

the other thing i found was the cheap relay boards sometimes have really noisy coils that backfeed into the 5v line when they switch, worth throwing a snubber diode across each relay coil if they dont already have them. most of the amazon ones do but you never know what youre actually getting.

honestly for just switching relays the pi is overkill like you said. i went down that road and ended up spending more time messing with linux stuff than actually doing radio. the arduino just works once you get the RF sorted out. one thing though — if you ever do want logging integration down the road you can always have the arduino talk to a pi over serial and let the pi handle the software side while arduino does the actual I/O. best of both worlds and keeps the sensitive electronics away from the RF mess near the antenna feedlines