so ive been messing around with an arduino mega for the past few weeks trying to build an automated antenna switcher for my shack. i've got like 5 antennas right now — a dipole for 40m, a vertical for 80/40, a 2m yagi, and a couple others — and im constantly reaching over to flip relays manually which is getting old real fast.

my idea is basically to have the arduino read which band im on from the radio (using a BCD output from my IC-7300, it does output band data on the ACC port) and then key the right relay automatically. i already wired up a little relay board i got off amazon, 8 channel one, and i can toggle relays fine from the arduino. the problem im running into is the logic side — reading the BCD lines and mapping them correctly to antenna choices isnt going as smooth as i thought. i keep getting false triggers when i switch bands rapidly.

has anybody done something similar? wondering if i need debouncing logic or if theres something smarter to do on the software side. also considered doing this with a raspberry pi instead but seems overkill for just switching relays. open to ideas though.

yeah the debouncing is almost definitely your problem. BCD outputs from radios can bounce around for a few milliseconds during a band change — the arduino is reading garbage in that window. what i did on a similar project was just add a small delay after detecting a change, like 50-100ms, and only act on it if the value is stable across multiple reads. not the most elegant solution but it works reliably.

also worth double-checking your grounds. if the arduino ground isnt tied to the radio ground youll get all kinds of weird behavior, especially if you have other stuff in the shack running off different outlets. i chased that one for two weekends before figuring it out. the relay board itself can also inject noise back into the arduino if you havent got the coil supply isolated — those cheap amazon boards usually dont have optical isolation even if they say they do.

i did almost exactly this with a pi zero a while back, and honestly the arduino is the right call for something this simple. pi has too much latency from the OS getting in the way if you want fast reliable IO. for just reading BCD and keying relays an arduino nano would even be enough, the mega is plenty.

one thing i'd add — put a manual override switch in parallel with each relay. there will be a day when the code does something dumb and you want to be able to switch antennas without rebooting everything mid-qso.