so ive been messing around with arduino for a few months now and got pretty comfortable with basic sketches and relay control and i keep thinking there has to be a good way to tie this into my shack setup. right now i have a manual coax switch for going between my 40m dipole and the vertical and honestly i keep forgetting to switch it and then wonder why my swr is awful for the first 5 minutes of a session lol

my thought is to use an arduino mega with a relay shield and somehow have it read which band im on from my rig and switch automatically. i have a kenwood ts-590sg which does have CAT control over usb so maybe i can have a raspberry pi handle the serial polling and then talk to the arduino over i2c or just send simple gpio signals. is that overcomplicating it or does that kind of setup actually make sense

i dont have a great electronics background, mostly self taught from youtube and a few projects, so if theres a way to do this without blowing up my radio id love to hear how people have approached it. also open to just doing it with a pi alone if the gpio is enough to drive the relays directly with a transistor or mosfet or whatever

yeah ive done basically exactly this, though with an icom but the principle is the same. the pi handles the CAT polling via hamlib - rigctld specifically - and then i just have a small python script that checks the frequency every couple seconds and writes to a gpio pin depending on the band. the relays i used were those cheap SRD-05VDC-SL-C ones off amazon, you do need a transistor and a flyback diode or you risk frying the gpio when the relay coil collapses, thats the part people skip and then wonder why their pi keeps browning out

honestly you dont really need the arduino in the loop at all for something this simple. the pi can handle it fine. where i would use an arduino is if you need hard realtime stuff or if you want to offload something so the pi doesnt have to babysit it constantly. for just antenna switching the pi alone is fine, hamlib is well documented and once you get rigctld running it's pretty straightforward to parse the frequency output

I went a slightly different route - I actually used a Nano instead of a Mega since I only needed a couple relays and didn't need all the extra pins. Ran it standalone without a Pi at all. Mine reads voltage on a sense line that I tapped off the band data output on my radio (older Yaesu has actual band data pins which makes it dead simple), but the CAT approach is probably smarter if your rig supports it cleanly.

One thing I'll throw out there - watch the relay ratings if you're switching anything with any meaningful RF on it. Those cheap relay shields aren't rated for RF and you can get arcing across the contacts at higher power. I keep mine to 100w or below and haven't had an issue but just something to be aware of depending on your setup.