[Milsurplus] BC-669 Project: More Transmit Crystal Subber Work

[David Stinson]

For the three people and one aardvark in the 
Universe interested:


I and Jeff Angus continue to work on a substitute for
expensive or unavailable crystals in our transmitters,
Jeff for his BC-610 and I for my current project,
a bunch of BC-669s.  
All that's needed for the receiver side of the rigs
is the programmable oscillators and a blocking cap.
Works great into the 6SA7 Hexode converter.

Not so easy with the 6L6 Crystal Oscilllator on the
transmit side.

I did some earlier work using
just a programmable oscillator, a 4:1 UNUN and 
some DC blocking caps.  This worked well for 
the "ARC-5" VHF transmitter and for a the little 
"type-12" transmitters.  However, it does not give
enough drive for most vintage crystal oscillators.
Jeff Angus and I have been working with a circuit 
derived from a June, 2011 article in CQ by WA1FFL.
Here's what I'm building.  Jeff's is similar:
https://goo.gl/photos/ftG8Aw1JJKBC6tas8

First prototype, working well on the bench:
https://goo.gl/photos/PYCVXLhiuYZYL2Dv5

Nearly finished and, with luck and time, will be
tested in the rig next week:
https://goo.gl/photos/ej3G3WbwYuH1cNGJA

The little green board is a wonder from Ebay.
DC-DC step-down converter, 5-28V in, adjustable
regulated 1-20V out.  3 Amps it will source.
About the size of a postage stamp.  

Cost?  78 CENTS.
You'll note the one in the breadboard has an
old crystal plate glued to it.  It did have a birdie
in a bad place.  I glued the plate on the little 
inductor and *poof,* no more birdie.

Will let y'all know how it turns out. 
Jeff's should work even better.

GL ES 73 OM DE Dave AB5S