Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Ken -
Just remembered I have a 2-B open on the bench. I assume you mean the
cap that is stretched across the "top" (bottom?) edge of the board.
That is the coupling capacitor between the two middle inductors, C34 on
the 2-A schematic. In the 2-A it's 27 pF, and in the R-4 series the
same cap is 5 pF. The difference in value is because the coupling
capacitor is varied by the bandwidth switching system. Without
analyzing the filter in the 2-A and trying to extrapolate the values to
a 3 b/w filter, I'd start with something around 15-20 pF and see if the
filter has a reasonable passband shape. The filters were swept at
Drake and that cap and the two on either side were picked as a part of
that alignment.
All that aside, it's probably going to take some fiddling to get the
right value. You might take a look at the Elecraft website and
"borrow" their filter alignment method. Basically it feeds a broadband
noise source into the front end of the receiver and looks at the audio
output spectrum with a computer sound card using a software package
called Spectrogram. Spectrogram is a shareware product and I think
there is a link on the Elecraft site to download it.
Let me know how you make out!!!!
73, Garey - K4OAH
Atlanta
Drake B & C-Line Service CDs
<http://www.k4oah.com>
Ken Kaplan wrote:
Ken Kaplan <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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I need some assistance in identifying a disc capacitor on my 2B.
Mounted on the passband selector switch, is a small disc capacitor,
connected to the two end connections on the terminal board. It has
some violet (paint) marking on it.
The schematic I have is very 'blurry' at the point I need to see.
I'll do a digital pix, if no-one can identify it.
thanks
73
Ken WB2ART
Sayville, NY
www.wb2art.com
www.unpcbs.com
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