[Elecraft] SSB Filter Bandwidth Control

Fri Jul 25 03:32:00 2003

The short answer is that the filters are "tuned" by selecting values of
voltage applied to each of the voltage-controlled varicaps in the filter .
Conventional ladder filter but with voltage-variable caps to tune it to
different bandwidths, etc. Clever way to get variable selectivity from one
set of crystals.

73/72, George
Amateur Radio W5YR -  the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"
<mailto:[email protected]>

----- Original Message -----
From: "William M. Spaulding, Sr." <[email protected]>
To: "Elecraft Reflector" <[email protected]>
Sent: Friday, July 25, 2003 1:43 AM
Subject: [Elecraft] SSB Filter Bandwidth Control

> Folks,
>
> 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.... ;-)
>
> Thanks for any insight.
>
> Bill
> NA7Y
>
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