Analog
VFO Notes
by
John Seboldt, K0JD,
Milwaukee,
WI |
Last update: 3/23/04
(format)
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The
Analog VFO's |
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...
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 rec.radio.amateur.homebrew and on the QRP mailing list qrp-l@lehigh.edu. 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...
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