[AMRadio] Protecting receiver (was WTB: Coax relay, 110VAC, aux contacts)

[Bernie Doran]

Hi Rick: I commonly use  a TPDT  so called ice cube relay rated at 10 Amp 
per contact and have found that they will carry anything I can run legally 
or otherwise at least on the low bands.    I always close them prior to the 
power being applied to the final stage, ( and open a short time after 
removal of power) another small relay is used to short the antenna terminals 
on the receiver, the mute, and also short the speakers.  Probably not a big 
issue with VT receivers but it does not hurt either.    I also have some six 
pole relays that are going to be used in a control box that will provide 
switched 28 DC, grounds and several open an closed circuits to control 
everything.
----- Original Message ----- 
From: "Rick Poole" <wa1rkt at arrl.net>
To: <amradio at mailman.qth.net>
Sent: Friday, November 18, 2011 6:09 PM
Subject: [AMRadio] Protecting receiver (was WTB: Coax relay, 110VAC,aux 
contacts)


>
> Someone here suggested that instead of a coax relay, I just get a
> DPDT 110-VAC relay and use that, and he suggested a Radio Shack part
> number.  So, today I stopped by the local Radio Shack and bought the 
> relay.
>
> Then it occurred to me... the relay gives me one set of contacts to
> switch the antenna from transmitter to receiver, and another set to
> connect to the Mute input on the receiver.  I'm wondering if I should
> have a third set of contacts to short out the receive antenna input
> during transmit and protect the receiver front end.  The receiver is
> a Hammarlund HQ-180A and the transmitter is a barefoot DX-100B... do
> I need any front end protection for the receiver?... perhaps a pair
> of back-to-back 1N4148-type diodes across the receiver RF input?
>
> Rick WA1RKT
>
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