|Subject:||Re: LF: Re: Antenna relays|
|From:||Andy Talbot <[email protected]>|
|Date:||Thu, 19 Nov 2015 12:44:00 +0000|
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|References:||<[email protected]> <[email protected]>|
You're forgetting the loading coil has to be switched out when using the loop at HF, so the relay has to withstand the full RF voltage when using it as a vertical at LF/MF.
So you'll need a vacuum relay with a contacts rated at something like 10kV. The current will only be an amp or so. I tried this once using FR / Crydom reed relays that were certainly rated at that sort of voltage. Trouble was that rating was DC. At 137kHz it died with a flash from inside and melted contacts as soon as a decent amount of RF was applied.
A knife switch on a ceramic former would probably work, otherwise find someone working for
NatGrid and try to get a 33 or 132kV contactor :-)
On 19 November 2015 at 12:24, Alan Melia <[email protected]> wrote:
Hi Chris I dont think the relay type is too significant at these frequencies. The important thing is its contacts should be able to carry the current. It is at a low impedance point so the voltages should not be excessive. Even an open frame style intended for switching 20 to 30A of 230v would be worth trying (I am sure you have a bin-full or two of those lying around :-)) ).......the old-timers used knife switches at these frequencies :-))
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