so ive been messing around with this idea for a while now and finally started putting something together on the bench. basically i want to use an arduino mega to handle all my antenna switching automatically based on band — right now i have a 40m dipole, a vertical for 20/15/10, and a loop thats kind of a wildcard. every time i change bands i have to physically reach over and flip the coax switch and honestly it drives me nuts especially during contests.

the plan is to tap into the band data output from my rig (its an ic-7300 so it does put out band info over USB via CI-V) and have the arduino read that and trigger the appropriate relay. ive already got a 4-relay module sitting here and a handful of logic level converters. the tricky part im running into is getting the CI-V parsing right — the icom protocol isnt super complicated but its not exactly plug and play either. anyone who has done something similar with a PI or arduino and icom rigs, how did you handle the band data parsing? did you use a library or just write your own state machine?

also a little worried about RF getting into the arduino and causing resets. ive seen that happen before with a different project and it was a nightmare to track down.

yeah i did almost exactly this with a pi zero W and an ic-7300 about two years ago. the CI-V stuff is doable but i ended up using a python library called pyserial and just polling the rig every 500ms or so for the operating frequency then mapping frequency ranges to relay states. its not elegant but it works and hasnt missed a beat. one thing — make sure you debounce or add a short delay before switching the relay because sometimes when you're tuning across bands the rig spits out a bunch of frequency updates fast and you dont want the relays chattering.

for RF i put ferrite beads on every line going into the arduino and wrapped the USB cable a few times through a big clamp-on ferrite. also grounded the arduino case to station ground. had one reset issue early on that went away after i added a 100uf cap on the 5v rail close to the board — probably just noise on the supply more than actual RF but it helped.

not done the icom ci-v thing specifically but ive built a few relay switching projects with arduino and the RF ingress problem is real. what i do now is just put everything in a diecast aluminum box and make sure the grounds are all tied together properly. cheap arduinos from aliexpress seem way more susceptible to this than genuine ones in my experience, not sure if thats the regulators or what but ive had better luck with genuine or at least the better clones.

one thing i'd think about — if the ic-7300 is on USB already for logging or whatever, you might hit COM port conflicts depending on your logging software. might be worth considering the separate ACC port or the remote jack instead if that fits your setup better. just something to be aware of