[Collins] E. F. Johnson T/R switch

[Jim Brannigan]

If you are using the 32S-3, I suspect you are hearing the low level RF 
signals, not the sidetone.
In STBY the 32S-3 T/R circuit reduces, but does not cut off the low level 
stages.

I ran across this after installing a 455.00 KC crystal in the 32S-3 CW 
position.
A few minor modifications to the T/R circuit solved the problem.

Jim


> Has anyone tried to incorporate the E. F. Johnson T/R switch into the 
> Collins S Line series 3?  The goal is having true break in keying. In 
> experimenting  with the idea I have run into a problem with hearing the 
> tone oscillator until  K1 drops out. The result, is after you let off the 
> cw key, you hear the tone generator at low level, then the K1 drops out 
> and you hear the receiver audio.
>
> I currently don't see any practical way to prevent this. I have no 
> intension's of making major modifications to the S Line. And the tone 
> generator is doing what it is suppose to do in cw, that is key the K1 
> relay via the attached triode and provide cw sidetone. I removed the cw 
> sidetone cable from the receiver but the tone generator is still audible.
>
> I am curious how the 750 cps tone generator is making it's way into the 
> audio path to the speaker. I defeat the receiver mute by place the 
> receiver function switch in the operate position instead of the normally 
> used standby position. The only other path I see is the tone generator 
> going into the balanced modulator. But during cw operation the rf signal 
> doesn't pass through the balanced modulator.
>
> Smith Bradford
> W9HAK