Return to KLUBNL.PL main page

[Top] [All Lists]

Re: LF: Re: Antenna relays

To: [email protected]
Subject: Re: LF: Re: Antenna relays
From: Andy Talbot <[email protected]>
Date: Thu, 19 Nov 2015 12:44:00 +0000
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=Rl4nDIrBxhQgdW+hQ4Pgh+J7n7Kh3vOGOrxgi+rZM6c=; b=ignu07fcjN6IKuxXMTYgpjM4A0wOxZVhx77LuYQo6KooAS/7B4IplkUW6nFleM3EiZ 5RLqN9ei1ksswB2tvrXBmepTDq6L+mCHeFKeWrYpFGoUOahs9gimLpJXn3g+CKJpj0Uv nOUOsaEdcckleNbEgr/LSY+YLB9PYBQLf55BHsEha4iGSKT/TN96QhP4YEHP6eQduoUy QyCJEAsbUBAof0s3ypP0MqXzolbvS/cVmrN8WuAlaWK8lHo0/2mjLhen10XQf+PI35kP p4799UFXIBccH509L9Nj2rZgrigt1E9xuckYbOp5RGQecmDpcdpAXbaToKxSh6x5TS7y t+ZQ==
In-reply-to: <[email protected]>
References: <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Alan - 
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 :-)

Andy  G4JNT

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 :-))


----- Original Message ----- From: "Chris Wilson" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 19, 2015 12:00 PM
Subject: LF: Antenna relays

19 November 2015

I am currently running a bottom strapped windowed ladder line feeder to
my  horizontal  quad  loop  as  the  vertical for LF, the loop as the
capacitive  top hat. It means I am unable to use it for HF though. I am
wondering if I might add a remote switched relay at the bottom of the
ladder line, so it has two states. One connects my co ax feeder to the
ladder  line  with  the  bottom strapped together. the other opens the
strap and connects the 2 legs to a balun and then my co as feed line.

Given  the voltages involved at LF, what sort of relay would I need to
be looking at? Thanks.


Best regards,
Chris  2E0ILY                           mailto:[email protected]

<Prev in Thread] Current Thread [Next in Thread>