Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

"Normal" relays at RF

Status
Not open for further replies.

avdrummerboy

Member level 2
Joined
Nov 10, 2006
Messages
49
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,622
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.

Any help/ advice greatly appreciated.
PK
 

Hello,

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.

Regards,
Frank
 

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.
 

Hello,

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.

Regards,

Frank
 

you need to use gas filled relays only at frequencies => 50mhz

if it was 2meters band yes a gas filled would be needed

but it sounds fine as long as you decouple any stray rf from the relays coils to ground

and dont switch it while your transmiting {a small delay can be built in using a cap or something}
 

Yeah I was going to put a diode and cap across the relay coils.
 

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.

Frank
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top