Fw: Fw: "SB"-Series AM Filter...PART # (Final)

[Edward Swynar VE3CUI]

Hi gang...

Jan was kind enough to also provide me with some dope re. the possible
cloning of Heath's OTHER rare entry into the i.f. filter scene, i.e. the
400-Hz CW filter...

I can see no reason whatsoever why this couln't be copied as readily as the
AM filter---all you need are the crystals, & the desire (as Capt. Pickard
would say), to "...Make it so"! Hi Hi.

~73~ Eddy VE3CUI - VE3XZ




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>
> ----------
> > From: n8lqr at juno.com
> > To: gswynar at durham.net
> > Subject: Re: Fw: "SB"-Series AM Filter...
> > Date: January 16, 2000 4:55 PM
> >
> > Hi Eddy:
> >
> > The small case CW filter is built the same as the small case AM filter.

> > The schematic diagrams are the same.  The top left crystal is 3395.450
> > kHz and the top right crystal is 3395.150 kHz.  The bottom left crystal
> > is 3395.150 kHz and the bottom right crystal is 3395.450 kHz.  Both
> > 3395.450 crystals have a 0.56 pF phenolic capacitor in parallel with
> > them, just like the AM filter.  The mica capacitor in parallel with the
> > adjustable, center-tapped coil is 47 pF however.  The coil is the same
as
> > in the AM filter: 115 uH slug tuned, center-tapped.  The circuit board
is
> > also the same as in the AM filter:  Heath part no. 85-157.
> >
> > The specifications for the CW filter crystals are:
> >      Effective series resistance:  25 ohms maximum
> >      Load capacitance:  35.4 pF
> >      Frequency tolerance:  + / - 50 Hz
> >
> > Interesting that I had the same thought that you did about the CW
filter:
> >  that it would be feasible to build one yourself by obtaining the
> > required parts.  I got the idea after looking at the blueprints for the
> > AM and CW crystals.  The CW filters are almost as scarce as the wide AM
> > filter, and more expensive.  My SB-313 does not have a CW filter; the
> > -301 does.
> >
> > >From your description of the SSB filter, I understand that the tapped
> > toroid coils with parallel ceramic trimmer capacitors take the place of
> > the adjustable center-tapped coil with parallel fixed capacitor used in
> > the CW and AM filters.  Is that right?
> >
> > My guess is that the center crystals in the SSB filter (3393.960 and
> > 3395.100 kHz) set the outer limits of the bandpass curve and make the
> > sides steeper.  I will look in my reference books to see if I can find
> > the circuit that Heath used.
> >
> > Jan Maldups, N8LQR
> > Kalamazoo, Mich.
> >
> >
> >
> >
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