Hey guys, I have finished the control box of my remote antenna switcher and am now on building the actual switch part. I have found some 10A 120VAC PCB relays at radshack for about $4.50 a pop. I was wondering if anyone knows what is different about these at RF, what kind of problems to expect. I have a $1800 Kenwood radio that I would rather not destroy (although the built in protection will probably cover me there.) Anyway, I figured that these 10A relays would be sufficient for the 100Watts output or less that I will be running.
I'm not particularly familiar with amateur radio issues, but I think it could be usable for SW (maybe with some limitations), but not usable for VHF and UHF bands. Basic problem is the contact inductivity causing impedance mismatching. For SW, the inductivity could probably be compensated by different "matchbox" tuning.
I was only planning on using it at HF (same basic range as SW.) Most PCB relays don't seem to look too good above about 150MHz. Once again they are small PCB relays, so the inductance shouldn't be much, but as I know it doesn't take all that much to ruin a signal.
with a Finder series 43 PCB relay (10A/250VAC contact rating), I found an contact inductance of about 12 nH from a rough measurement. I think, this should be the essential impedance component to be regarded below 150 MHz. The relay has 15 mm case height, older "high profile" relays could be expected to have longer contact legs and thus higher inductance.
Low power GHz relays are often coaxial reed type, high power HF relays are rather classical electromechanic type, e. g. various relays from Tohutso, Japan. See distributor www.rfparts.com/coaxial.html for reference.