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
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