[TenTec] How dioes one modify a crystal flter?

[Dr. Gerald N. Johnson]

On Thu, 2007-01-11 at 11:04 -0500, Craig Roberts wrote:
> Gurus,
> 
> I have a spare 2.4 KHz SSB crystal filter for my Argosy II and would 
> like to narrow its bandwidth to 1.8 KHz (or thereabouts).  Has anyone 
> done this?  How? (I'm guessing I could order crystals from Ten Tec).
> 
> Thanks and 73,
> 
> Craig
> W3CRR
> 
Its a combination of crystals and capacitors that set the bandwidth. Its
probably more profitable to buy the whole filter from TT or Inrad. But
to do it at home, go hunt up QST, and Handbook articles on ladder
crystal filter designs. Measure the individual crystals and apply the
design techniques to pick out new capacitor values. I think MFJ sells a
paper back book on the topic too. Or experiment by increasing the values
of the capacitors, which should narrow the bandwidth. With crystal
calibrator and the PTO you can measure the results in the radio.
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer