so ive been messing around with a little arduino mega project for the past few weeks and i think im finally getting somewhere. the idea is pretty simple, i want to automatically switch between my hex beam and a 40m dipole based on which band i tune to on the radio. right now i'm using a CAT interface on my 7300 and reading the frequency data off the serial port, which actually works better than i expected once i sorted out the baud rate mismatch that was making everything garbage.

the relay board i picked up off amazon is a 8 channel 5v unit and it seems okay so far but i havent pushed it hard yet. my concern is whether running coax through those relays is going to cause any issues at 100w, the specs on the board are kind of vague and i honestly dont trust the chinese datasheet on this one. thinking about maybe swapping to some proper RF relays at some point but wanted to get the logic working first.

anyone done something similar? especially curious if anyone has done the CAT parsing on arduino because there's a lot of conflicting info out there about CI-V timing and i've had some weird lockup issues that i cant fully explain yet

yeah i did almost exactly this about two years ago with an uno and an IC-7100. the CI-V stuff on icom radios can be a pain because its half duplex and if your timing is even slightly off the radio just stops responding. what worked for me was adding a pretty generous delay after sending any command before i tried to read back, like 50ms or more felt excessive but it stopped the lockups. also make sure your address byte is right, the 7300 might be different from the 7100 but same idea.

on the relay question — i wouldnt run 100w through those cheap amazon relay boards. the contacts are rated for AC mains current which sounds like a lot but RF is a different story, the contact geometry isnt designed for it and you can get arcing especially on SSB peaks. i eventually swapped to some surplus omron RF relays i found on ebay and the difference in feel was noticeable, coax connectors on them and everything. worth the effort if you're going to use this seriously.

i did something similar but went with a raspberry pi instead because i wanted a web interface so i could see what was going on from the shack PC. ended up being way more complicated than i planned lol. the pi is nice for that kind of thing but honestly for just reading CAT data and flipping relays an arduino is probably the smarter choice, less overhead and it just runs, no waiting for linux to boot or worrying about SD card corruption which has bit me twice now