[Elecraft] K2 AGC/S-meter calibration - cw vs. ssb

[Dale Boresz]

Don,

Thanks for your suggestions. I did a little experimenting, and thought 
I'd post the results back to the reflector.

I happen to have a second KSB2 modified for a 2.2KHz bandwidth, while my 
primary KSB2 is modified for the 2.5KHz bandwidth. The KSB2 with the 
narrower bandwidth produces 1 S-meter bar more than CW mode,  and the 
KSB2 with the wider bandwidth produces 2 S-meter bars more than in CW 
mode.  Perhaps a standard, unmodified KSB2 board would not show the 
disparity at all - but I'm not 'unmodifying' either of mine to find out.

I just recently built the 2.2KHz KSB2, and at that time had grounded the 
xtals at the bottom rather than at the top. I modified the 2.5KHz KSB2 
by grounding those xtals at the bottom as well, but there was no 
noticeable difference.

The I.F. xtals have always been grounded at the bottom, on two sides of 
the cases, and when I used the XG1 to measure the MDS of the K2, the 
result was -139 dBm, so I think all is well with the I.F. filter.

In summary, judging by the responses posted by several other 
Elecrafters, it would appear that I am not the only one who has 
experienced this. But I don't consider it to be a problem, and I'm very 
pleased with the performance of my K2 in both cw and ssb modes. In fact 
maybe this should be considered a 'feature'. With the S-meter optimized 
for cw mode, the slightly elevated readings observed in ssb mode will be 
more compatible with the inflated S-meter readings occasionally heard to 
be handed out in the phone bands.   :-)

Thanks also, to Tom and Stewart for your reponses.

Don Wilhelm wrote:

>Dale,
>
>I can think of a few things that could cause a change from CW to SSB.
>For one thing, the wider filter does let more total energy through, and the
>ALC and S-meter respond to that total energy.  ...
>
>It could be that you have a filter blow-by increase when the SSB filter is
>selected.  ...
>
>I have found on several K2s that grounding the IF crystals very near the
>bottom on both sides helps this (noise floor) condition, and grounding the
>SSB crystals near the bottom also helps ...
>
>Once the crystals are grounded, you can do measurements with the XG1 to set
>S9 at 50 uV for various combinations of AGC Threshold settings, CAL S Lo and
>CAL S Hi.  ...
>
>73,
>Don W3FPR
>
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