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

[Bob K6UJ]

Heres what I used for a TR switch on my boat anchor AM station. Very easy to make and it works fine.
I am using a Collins R388 and a Viking 2.  The Viking 2 has 110V contacts available for a TR switch.
And yes you need another set of contacts to mute the receiver so a DPDT relay is the answer.

http://www.ad5x.com/images/Articles/AntennaRelay.pdf

73,
Bob
K6UJ






On Nov 18, 2011, at 4:09 PM, Eddy Swynar wrote:

> 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
> 
> 
> *********************************************************************************************************************
> 
> 
> 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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