[Elecraft] K2 Crystal Filter Alignment Questions

[Tom Hammond]

>On Aug 19, 2006, at 1:52 AM, Jeff wrote:
>
>>Finally, and most irritatingly of all, in CW mode, when I switch
>>from filter FL1 to FL2, the pitch of the received CW signal changes 
>>significantly. However, when I switch from FL2 to FL3, or from FL3 
>>to FL4, no such pitch change occurs, which is good.
>
>The K2 design isn't perfect in this regard, because of the way the
>BFO frequencies are determined - but you should be able to get any
>shift down to a few Hz, if that.
>
>It sounds to me like you don't quite have the filters aligned correctly.

My guess is that IF the CW note changes SIGNIFICANTLY between FL1 and 
FL2, then you probably have the BFO setting on the WRONG SIDE of 
filter-center. This is not an uncommon problem. Fortunately, it is 
one which can be easily fixed... especially if you are using 
Spectrogram and IF you follow the published instructions, BOTH of 
which are available FOR FREE at www.n0ss.net.

The important thing is to know which sideband (CW NOR or CW REV) 
you're aligning, and then ensuring that the BFO is always positioned 
to the proper sideband (either above or below the center frequency of 
the filter).

>>Shouldn't I be able to correct this problem by trial-and-error,
>>without using Spectrogram?
>
>Yes, I've done this. Try moving a filter one step up or down from
>where Spectrogram thinks it should be. See if it makes things better
>or worse.

It CAN be corrected by trial & error, but it's a WHALE OF A LOT 
EASIER if you do use Spectrogram.

>>Unfortunately, I'm not set up to use Spectrogram to align the filters.

What are the problems to setting up TO use it?

73,

Tom Hammond   N0SS