so ive been messing around with this idea for a few weeks now and finally started putting something together. basically i have 4 antennas and im tired of going out to the shack and manually flipping the coax switches every time i want to change bands. figured an arduino with a relay board could handle the switching and i could just control it over serial or maybe even a little web interface if i throw a pi in there too.

right now ive got a nano running a basic sketch that listens on serial and triggers the corresponding relay. works fine on the bench, the relays click and everything seems solid. my question is about the RF side of things — the relays im using are just generic SRD-05VDC-SL-C from ebay, like the ones that come on those blue relay boards. at HF power levels are these going to be okay or am i asking for trouble. running about 100w most of the time, sometimes up to 500w on a linear. i know there are proper RF relays but they're not cheap and im wondering if anyone has just... used the cheap ones and survived.

also if anyone has tied a pi into something like this for a web interface i'd love to see how you wired it up. i dont really want to reinvent the wheel if theres already a good approach floating around.

yeah those SRD relays are not really rated for RF switching at power, the contacts arent designed for it and youll get arcing especially if you ever switch under load which you absolutely should not do anyway but still. i fried a couple of those experimenting with a similar setup and at 500w on a linear im not even sure they'd survive a few switching cycles before the contacts get pitted. for HF antenna switching the usual go-to is vacuum relays or at least the hamfest special coax relays that are meant for it.

that said for 100w casual use some people do get away with it for a while. just dont switch hot. ever. the arduino part sounds solid though, i did basically the same thing with a mega and a 8 channel relay board to sequence my amps and accessories and it works great for that kind of low voltage logic stuff. just be careful where you route the signal lines near the RF path or youll pick up noise in weird places.

for the pi web interface thing — look up hamlib and flrig, you might be able to tie into those rather than writing everything from scratch. i have a pi zero w sitting between my rig and the network mostly for remote operation stuff and it wasnt that hard to get a basic control page going with flask. nothing fancy but it works over the local network just fine. the tricky part for me was getting the serial timing right so commands didnt stack up and cause the arduino to miss inputs.