Analog VFO Notes

by John Seboldt, K0JD, 
Milwaukee, WI

Last update: 3/23/04

The Analog VFO's
t36t8vfo pic

Updated boatanchor analog frequency control (above): My main analog VFO is a transistorized military surplus T-368 exciter, a very stable VFO and mechanical digital dial for 1.5-24 MHz. I had gotten this years ago, and used it with my Heath DX-60 with its original tubes. As I got into the homebrew scene, I thought this would be a fine basis for the hardest-to-make part of the rig. Part of me wonders now about gutting such classic tube gear, but at least my exciter is still used when others are probably buried in landfills... 
  • t368vfo
  • Update on my addition of another varicap and pot for fine tuning
  • hcbuffer, description of a VFO buffer based on a 74HC240 chip 
Though this is my ultimate analog stability standard, one must at times build something more compact for use outside the shack. My pursuit of good stability -- toroids vs. air coils, temperature compensation, etc. -- got this nice VFO Stability thread going on and on the QRP mailing list This finally led to satisfactory stability at 7 MHz in a rather compact box, described here. It's part of my JD Journey Box -- A 40/20m CW rig based on the miniR2. 

This feels so satisfyingly "analog," that I've taken my time moving into other frequency control methods. But time marches on with various experiments...

John's Mugshot

John Seboldt, K0JD, Milwaukee, WI
  • Email to: k0jd at seboldt dot net (not spamfoil - translate to standard e-mail-ese ;-) )
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