[Elecraft] How to center K1's crystal filters?

[Don Wilhelm]

Unlike the K2, you will not center each of the K1 filters.
Set the K1 IF filter to the narrowest one - FL3 unless you have made 
some filter width changes from the normal defaults.
Then adjust the BFO trimmer (C20) to position the center of that 
narrowest filter at your chosen sidetone pitch as indicated on your 
audio spectrum analyzer.
Then remove the bottom panel and set S2 to the TEST position. Adjust C13 
to place the signal at your chosen sidetone pitch - that sets the 
Transmit Offset.
Return the S2 switch to the OPR position and you are done.

Make certain you set the menu STP parameter to your chosen sidetone 
pitch so you can do SPOT at the same frequency.

The exact center frequency may not track exactly for filters greater 
than the most narrow, but will result in a very usable received sidetone 
pitch for any of the filter widths.  In other words, the filter width 
may increase more on the high audio frequency side than on the low 
frequency side, but the peak of the filter will remain at the pitch 
obtained by aligning with the filter set to the narrowest setting that 
you will use.

73,
Don W3FPR

On 1/25/2016 7:17 PM, cottersay wrote:
> I built my K1 years ago, but I also just re-read the K1 manual, yet I still
> do not quite understand how to adjust the Xtal filter's bandwidth to center
> on my chosen sidetone frequency of 500Hz.  (The way I check the K1's xtal
> filter's center frequency is to display the K1's audio output noise into a
> PC's spectrum analyzer, as shown below).
>
>