[Elecraft] K2 filters charactoristics

[Don Wilhelm]

Neil,

That is NOT the way it is with the K2 at all.

Through the K2 menu, CAL FIL function, you are able to adjust the variable
bandpass filter to any width that you want, AND adjust the related BFO
frequencies to place the passband anywhere within the audio range that you
would like it to be - most folks do center the CW filters at their chosen
sidetone pitch (SPOT frequency) as you would like to have it set.

The manual settings will get you in the ballpark, but to more properly place
the BFO frquencies, feed the K2 antenna input with a wideband noise source
(Elecraft N-gen is preferred or an antenna wire laid alongside a lighted
flourescent lamp should provide an adequate source of wideband noise - do
not use a single frequency signal, it will confuse things), then use an
audio spectrum analyzer (Spectrogram, Hamscope, etc.) to view the resultant
audio passband response.  With the K2 menu set for CAL FIL (and the K2
frequency probe plugged into TP2), you can adjust the BFO to place the
center of the passband at most any audio frequency that you want - ideally
your chosen sidetone pitch.

For additional information and helpful links on how to accomplish the
filter/BFO alignment for both CW and SSB, look at the K2 Dial Calibration
article on my website www.qsl.net/w3fpr - Step 3 is the CAL FIL procedure
that you are interested in.

73,
Don W3FPR

----- Original Message ----- 
>
> I have done the filter alignment on my K2  S/N 4215 as per the procedure
in
> the manual and
> my numbers match the manuals numbers.  When I look at the filter
presentation
> on Hamscope
> I notice that all the four filters have the correct band width, but as you
go
> from wide to narrow
> the change in band width is only changed at the high frequency end.  So if
> you have a SPOT
> frequency of say 700 cps. the tone would be fine in the 1.5K B/W filter,
on
> the edge and weak
> in the 700cps. filter, and not heard on the remaining narrow filters.  If
you
> change the SPOT
> frequency to 400 cps. it can be heard on all of the filters.
>
> What this says also is the SPOT frequency can never be higher than the
> narrowest filter if you
> want to hear it.
>
> Is this the way it is using the K2?
>