[Elecraft] K3 in a cw pileup - needs work

[Geoffrey Mackenzie-Kennedy]

Hi Guy,

The problem reported has the classic characteristics of in-passband IMD 
caused by a small dynamic range (IMDDR3) IF system, rather than being 
something caused by the AGC sub-system. Yes changing the AGC's loop 
characteristics will alter the effect, but the root cause is still 
non-linearity in the signal path. I suspect the second mixer.

Trouble is that large IMDDR3 IF systems can consume a lot of power, and low 
power drain by the K3's receiver was a design goal I believe.

73,

Geoff
GM4ESD


On Saturday, February 06, 2010 at 5:17 AM, Guy Olinger K2AV wrote:



> Hi Dave,
>
> Using slope 000 is likely most of your problem.  With that setting all
> signals regardless of strength are set to the same level regardless of
> how loud they are coming in.  If they are zero beat or close, it will
> mush the dickens out of the copy by making them all the same level in
> your ear. I set AGC SLP to 15 for contests.  I also use slow AGC the
> entire time. If there are key clicks, I use NB with IF off and dsp to
> t3-7 or t2-7.  It rounds off CW bauds some but does not make them
> uncopyable.
>
> Make sure your ATT/PRE/RFGAIN use conforms to something like:
>
> 160m ATT plus RF gain at 2 oclock
> 80m  ATT plus RF gain at 3 oclock
> 40m  ATT plus RF gain fully clockwise.
> 20m       "    "
> 15m  off plus RF gain fully clockwise.
> 10m  PRE plus RF gain fully clockwise.
> 6m        "    "
>
> ...if you are listening on your transmit antenna. At least to start.
> Make sure the ambient noise on the band is moderately low audio
> listening on a clear frequency.
>
> Using the NB with those settings, including the ATT/PRE/RFGAIN
> settings. Just today I was listening to an S4 Cuban underneath what
> were S9/5 key clicks with the NB off. Offending station up 500 Hz at
> 30 over 9 (really), and was using 250 filter running at WIDTH 350.
>
> Good luck in Sprint this weekend!
>
> 73, Guy.