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Wednesday, November 13, 2013

BITX Build Update #19 Layout, VXO, Bal Mod, Filter, PA

The files of the BITX20 Yahoo group were very useful to me during my BITX build.  So I have decided to make a contribution myself.  I uploaded a few drawings today.  Here is how I laid out the circuitry on my 8 inch by 11 inch copper clad board.  I included the isolation (Manhattan) pads for one of the bidirectional amps.   

Here is the VXO.   I built is on a separate board, but I could have put it on the main board. 

Here is the balanced modulator and crystal filter. 


Here is the power amplifier circuitry.  Amazingly easy to stabilize. 

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  1. what JFETs did you use on the VXO?

  2. The VXO oscillator has 1 mH RFC which I recall, DemAw use a lot.
    SRF is < 1 MHz and not so good for 23 mhZ oscillator. Just 5-10 mickrohenry all is what needed.

    Verdeep Singla

  3. Verdeep: Thanks. That may help explain the low freq oscillation problem I had. For now, the 1mH choke is working OK, so I'll leave it in mine, but I'll update the drawing. 73 Bill

  4. Bill,
    Which CAD package did you use to get that hand-drawn look.

    I like it!

  5. I use PencilPAD (tm). It is not really "cutting edge." It is more "sharpened edge." Perfect for discrete, analog, HDR projects.


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