[600MRG] WD2XSH/20

[Bill Cromwell]

On 11/10/2013 02:30 PM, Rudy Severns wrote:
> ------snip--
>
> One additional comment.  A couple of days ago I mentioned my 
> amplifier, when on but not transmitting, was injecting noise into the 
> main antenna which then was picked up by the rx antenna.  I wondered 
> why I hadn't noticed this before.  It turns out that the local noise 
> completely drowns out the amplifier noise except when the local 
> villain is either off or at least has drifted well up the band.  The 
> amplifier noise I can fix easily with a relay that grounds the 
> transmit antenna while receiving.  The noise is not due to fan brushes 
> arcing but is the kind of noise you when a transistor is biased on for 
> linear operation.  My amplifier has 55 dB of gain so any small noise 
> can be greatly amplified.
>
> 73, Rudy

Hi Rudy,

I have and use an electronic T-R switch here on HF both tube based and 
solid state and I have used them with both tube and transistor finals. 
If the finals are left powered and are conducting any idling current 
they will generate noise that will be be heard in the receiver. Your 
relay scheme to short the output (noise) to ground during receive will 
probably do the trick. For QSK CW or electronic T-R switching blocked 
grid keying (or the SS equivalent) will also take care of it (no idle 
current). It isn't just "your" TX final that does this.

73,

Bill  KU8H