[Amps] KiloVac HC4 Relays

[Roger Parsons]

Last month I posed a question about using these relays for RF switching even though they are not specifically rated for that purpose.

The general consensus of the replies was that they would be OK although there was some fairly convincing anecdotal evidence that contact resistance would increase with time especially on the 'receive' contacts.

I have done a fair bit more research looking at the websites of all the vacuum relay manufacturers and elsewhere and I am now convinced that they _can_ be used for rf switching. The contacts are made of tungsten compared with copper for normal rf vacuum relays, which means that they have a slightly higher resistance which in turn reduces their power handling capability. However, that power handling capability is still 5 kW in 50 Ohms...

The relays that _cannot_ be used at rf are the gas filled versions as the rf will ionise the gas with bad results! 

I actually cannot work out why the contact resistance of a vacuum relay should ever change if it is not hot switched or overheated - there cannot by definition be any oxidation in a vacuum.

In case anyone else is interested I got the relays from:

http://apexelectronic.com/Rf.htm 

He gave me a discount because I bought 8 of them, but even his one off price is pretty good. (I have no connection with Apex Electronic but it was a pleasure to deal with them.)

73 Roger
VE3ZI