so ive been sitting on this idea for a while now and finally starting to actually do something about it. basically i have four antennas out back — a dipole, a vertical, a small loop for 40m, and a two element yagi that i built last summer — and right now im just using a cheap manual coax switch to hop between them which means i have to walk over to the shelf every time i want to change. annoying when youre in the middle of a pile-up.

my plan is to use an arduino mega with some relays to handle switching based on whatever band i select on my rig. the radio is an IC-7300 so i can pull band data off the ACC port, which should make it pretty straightforward to decode and feed into the arduino logic. i found a few sketches online but none of them are exactly what i need and my C++ is pretty rusty honestly.

has anyone actually done something like this or something close? curious if the relay noise is an issue or if i need to go solid state for the RF switching part. the coax relays i was looking at are like the Tohtsu kind, they handle the RF and the arduino just drives the control voltage. seems doable but im probably missing something obvious

yeah i did almost the exact same thing about two years ago, except i used a Uno and only had three antennas to deal with. the band data off the 7300 ACC port is pretty clean, its just a BCD output so decoding it in the arduino is like ten lines of code once you understand the pinout. icom has it documented in the manual but it took me a while to find the right page.

on the relay question — dont try to switch RF with normal PCB relays, you already seem to know this but yeah, those Tohtsu CX-series ones are the way to go. the arduino just needs to trigger a small transistor to drive the coil, and you want a flyback diode on each relay coil or youll get weird resets when they switch. ask me how i know. the noise thing isnt really an issue if the RF switching is handled by the proper coax relays and the arduino is just doing low-voltage control stuff.

one thing i added later that was worth it — a small 16x2 LCD so i can see at a glance which antenna is active. took maybe an hour to add and the library makes it dead simple.

not done it myself but a guy in our club built something like this with a raspberry pi instead of arduino, mainly because he wanted a web interface so he could switch antennas from his phone while sitting in the shack. overkill maybe but it was pretty slick. he used GPIO pins through a relay board from amazon, the whole thing cost him like 20 bucks in parts.

i think the pi approach makes more sense if you want logging or any kind of network integration, arduino if you just want something dumb and reliable that turns on when power comes up and does its thing. both are fine really depends what you want out of it