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

[Eddy Swynar]

Hi Rick,

Any T/R relay system that I've ever built here has ALWAYS shorted the receiver's antenna input when transmitting---that's especially important in modern-day set-ups (like ICOMS), where if you don't short the auxilliary antenna port, damage to the receiver can occur...to say nothing of distortion in your transmitted signal.

~73~ de Eddy VE3CUI - VE3XZ


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On 2011-11-18, at 6:09 PM, Rick Poole wrote:

> 
> 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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