so ive been messing around with this idea for a few weeks now and finally got something working well enough to talk about. basically i have a hexbeam and a couple verticals out back and switching between them manually is kind of a pain especially when im in the middle of a pileup and need to quickly jump between HF and 40m vertical. the shack PC already runs flrig so i figured why not get an arduino in the loop to handle the relay switching based on band data coming from the radio.

i went with an arduino mega because i needed the extra GPIO pins and didnt want to deal with multiplexing. wrote a simple sketch that listens on the serial port for CAT data, parses the band, and then fires the appropriate relay. added a small oled display from an old project just to show which antenna is active. worked first try which honestly surprised me.

the relay board is just one of those 8 channel jobbies from amazon, 5v coils so it plays nice with the mega without a level shifter. only thing i ran into is the relay switching transients were causing the arduino to reset occasionally - ended up putting a 100uf cap across the 5v rail on the arduino side and that seems to have fixed it mostly. might add a small ferrite on the power leads too.

anyway if anyones done something similar id love to see how you handled the interfacing side. also wondering if anyone has switched to a pi for this kind of thing instead - seems like overkill for just relay switching but i know some people run wsjtx or JS8Call on a pi so maybe bundling it all makes sense

yeah i did almost exactly this about two years ago but used a pi zero W instead of arduino just because i already had one sitting around. ran a python script that polls rigctld over localhost and switches a GPIO-controlled relay board. honestly the pi is probably overkill for pure antenna switching like you said but since it was already handling the logging sync and a few other things it made sense to bundle it.

the relay transient thing is real - i had the same reset problem. ferrite helped a little but what actually fixed it for me was using optoisolated relay boards. bit more money but completely killed the issue. the ones with the JD-VCC jumper you can separate the relay coil power from the logic power and that makes a big difference. definitely worth it if youre still getting occasional resets.

one thing to watch out for if you ever go the pi route - SD card corruption if power drops while its writing. lost a config once that way. just run it diskless or at least mount the filesystem read-only if you can get away with it.

nice, this is the kind of project i keep meaning to do but never get around to. quick question - how are you handling the antenna lines through the relay board? like did you put the coax through the relays directly or are you switching some kind of control voltage to a separate coax switch? asking because i tried running RF through cheap relay contacts once and it did not go well above like 14mhz, the contacts are not rated for much and i was getting weird SWR readings