[Elecraft] SSB Filter Bandwidth Control

[Don Wilhelm]

Bill,

You didn't miss anything - the OP1 (SSB) filter is not adjustable for
bandwidth.  If you want narrower filters for SSB, you will ue the varaible
filter on the RF board, and if you want to shift the audio range of the
demodulated SSB signal, you can set up for 'discrete passband tuning' if you
prefer.  You do have control over the BFO frequencies via the menu commands,
so you can adjust the BFOs  to suit your requirements - one does that when
setting up the filters and the use of a spectrum display (like Spectrogram
running on your PC) and a wideband noise generator makes it easy.

Any of the filter positions (there are 4 for each mode - CW, SSB, and
RTTY=data when enabled) can be used with either the variable filter on the
base RF board or the OP1 filter on the SSB board.  There are 2 BFO
frequencies associated with each filter, so up to 12 filters to select and
24 BFO frequencies to set in the process of setting up the full complement
of filters on the K2.  The only catch is that the K2 uses the SSB FL1 BFO
frequencies when transmitting in SSB mode, so you set those for best
transmitted audio, and you are free to set the others to suit your ears for
what you perceive as best receive characteristics.
Once set, you won't change them on any regular basis - only when you want to
make a change to your settings.

73,
Don W3FPR

----- Original Message -----
>
> I have a "how does that work" question.  After all, I think there is huge
> benefit to building a K2 just from the education you are forced to get to
be
> a successful builder and alignment tech.
>
> How is bandwidth control for the SSB filters accomplished.  I see NO
> hardware that can alter the frequency of the filter string on the SSB
board.
> I may have missed something.  In OP1, the CW crystal filter is bypassed,
as
> I understand it.  So, what is done in software to adjust bandwidth?  Is it
a
> stored look-up table to change shift the BFO and adjust the VFO to
> compensate for center frequency?????????  Or does the Control Board do
> things at audio to change the bandwidth of the signal content you hear?
>
> The roof won't fall in if I don't get an answer, but it will haunt me past
> the grave if I don't.... ;-)
>