[Elecraft] K3 receiver desensing on CW during contest

[K2MK]

Hi Bill:

Here are my CONFIG settings related to the AGC. The only ones I played with 
during the contest were SLP and THR. I always use AGC-F but did occasionally 
try AGC-S.

AGC-HOLD   000
AGC-PLS   NOR
AGC-SLP   010
AGC-THR   005
AGC-F   120
AGC-S   020

The differing conditions I described were the situation of everyone calling 
the DX close to his frequency versus one strong station calling 70Hz off 
frequency. When even strong stations called the DX right on frequency I was 
able to hear signals through the QRM. When strong stations called 70Hz off 
of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second 
to recover after he stopped sending.

73,
Mike K2MK



Bill W4ZV
Mon, 23 Feb 2009 05:31:37 -0800


K2MK wrote:
>
> I thought it was interesting that recovery was noticeably slow on the DX
> station's frequency when this was happening. However, under normal
> conditions when US stations were calling directly on top of the DX
> station,
> recovery was fast. Hence the ability to copy the DX station through the
> dits
> when the QRM was on frequency.
>

Mike this definitely sounds like desense but I'm surprised you experienced
it with only S8-9 signals.  I'm not sure what you mean about differing
conditions on and off the center frequency.  Desense will affect everything
inside the roofing filter.

What speed AGC were you using (F or S) and what were your AGC-F and AGC-S
CONFIG settings?  I NEVER use AGC-S on either CW or SSB and like at least
120 dB/sec for AGC-F.  Also, help your AGC do its job by not running RF GAIN
fully clockwise (as mentioned in my previous message).

73,  Bill