[R-390] break-in question, 390A and 390

[rbethman]

Amen!  It took a bit to figure that one out.

What was very startling, was to have the R-390A off the antenna switch 
with only about a 3 ft jumper of coax attached.  Somone across town lit 
up on the frequency and I swear the R-390A darn near jumped up!

Yes - they ARE that sensitive!

I've managed to eliminate the extra relay by using a Johnson T-R Switch, 
and using the break-in.

I monitor MY signal AND the one I am listening to by picking the 455Kc 
off the rear and feeding it into a Kenwood SM-220 w/BP-8.

Bob - N0DGN

On 7/24/2011 11:33 AM, David C. Hallam wrote:
> The break in relay on the R-390 only grounds the antenna input and does
> not mute the receiver.  What you have to do is open the RF gain
> connection on the back panel strip.  I did it with a relay.  On transmit
> you ground the R-390 break in relay and open the relay in the RF gain
> circuit.
>
> David
> KW4DH
>
> On 7/24/2011 10:42 AM, frankshughes at aim.com wrote:
>> Hi,
>> I am seeking advice on break-in function and troubleshooting audio.
>>
>>
>> I have a Collins 32S-3 transmitter, and am trying to use either a 390A or 390
>> to receive.
>>
>>
>> I have deduced that the relay logic for the 32S-3 (Open w/ PTT) had to be reversed
>> to work with the "break in" contact on the 390A and 390 terminal strip (N.O.)
>>
>>
>> So I put a relay in the circuit between the 32S-3 and 390, works great.
>>
>>
>> The ohm meter shows that when I PTT the 32S-3, the 390A and the 390
>> antenna input center pin goes to ground, and the audio also squelches to full quiet.
>>
>>
>> However, I get lots of audio output from the 390A and the 390 when I speak into the mic!!!
>>
>>
>> So even though the antenna input is grounded, both the 390A and the 390 are still getting
>> signal input.
>>
>>
>> The audio is also present from the 390 and 390A if I disconnect the antenna and activate break in
>> while keying the 32S-3.
>>
>>
>> Is the 32S-3 bleeding RF into the shack the 390 and 390A can pick up even with the antenna disconnected?
>> (How can these things be so sensitive to tiny RF levels...oh, wait....)
>>
>>
>> If so, building a Faraday cage around my transmitting position would be ....crazy.....OK, plan "B" is to
>> put a relay into the audio circuit to open the input to the speaker at the same time PTT is activating
>> break-in.
>>
>>
>> Or what else can I do????
>>
>>
>> Thanks,
>> Frank
>> KJ4OLL
>>