[Elecraft] K2 CW filter alignment

[Tom Hammond]

Hi Sam:

>I really didn't want to get into the in depth BFO alignment stuff 
>yet and am hopefully assuming it's on the correct side. My question 
>arose when I wanted to move the previous owners cw center frequency 
>up from 500hz to 600hz. Using the instructions I found on: 
>http://www.n0ss.net/k2_filters_using_gram_v5r17.pdf
>
>Everything went well, the center frequency is now 600hz and the 
>filters look and sound nice and tight.
>
>Referencing page 8 of the above pdf I ran in to a problem, so it 
>says. The DAC in CW Normal does is not lower than the determined 
>center frequency value.
>
>Then I read on page 9 and it says *if* the BFO is on the wrong side, 
>(which the DAC readings would seem to indicate), one or more filter 
>setting would show a shift of the center freq and be more than 200hz 
>off. All the filter settings are dead on, no vfo changes needed when 
>cycling thru the 4 settings.

The BFO center frequencies shift downward as the bandwidth is 
narrowed, so you must determine where 'center' is for each bandwidth. 
Then, the CW Normal DAC/Freq. values should ALL be below the filter 
center freq determined for EACH bandwidth selected. And the CW 
Reverse DAC/Freq. values should all be above filter center.

If you can change bandwidths and not have to re-tune the VFO to 
'find' the station, chances are that everything is A-OK.

However, once the filters are aligned for a selected sidetone 
frequency, if you change the sidetone freq. the filters will NOT 
automatically 'track' the change, you must re-align to the new 
sidetone freq. Some folks got the mistaken impression that tracking 
was automatic, and it's not.

>SO what's the deal here, do I ignore the DAC readings?
>Bandwidths used are 1400, 800, 400, 100.
>
>Center freq DAO                              CW Normal DAO
>142                                                   157
>135                                                   154
>130                                                   152
>128                                                   151

These values might well be CORRECT if you are performing the 
alignment on 15M and above, but they should be wrong if you are 
performing the alignment on bands below 15M. The recommended band for 
performing CAL FIL is 40M.

>Ah the joys of a rig you can actually work on, heheheh.

Hope this helps. If not gimme a SHOUT!

73,

Tom Hammond    N0SS