On Tue, 18 Jan 2005 06:08:14 GMT, "COLIN LAMB"
wrote:

Years ago, I decided to convert one of my Millen tube jobs to a solid state
one

When I got done, the 2 highest bands were off calibration.

That's because the inter-electrode capacitance of the tube is part of
the tuned circuit.

Dale H. Cook, Chief Engineer, WWWR Roanoke VA, WCQV Moneta VA, WKBA
WZZI Vinton VA, WKPA WLNI WZZU Lynchburg VA, WMNA/WMNA-FM Gretna VA,
WOWZ Appomattox VA
http://members.cox.net/dalehcook/starcity.shtml

Dale H. Cook ) writes:
On Tue, 18 Jan 2005 06:08:14 GMT, "COLIN LAMB"
wrote:

Years ago, I decided to convert one of my Millen tube jobs to a solid state
one

When I got done, the 2 highest bands were off calibration.

That's because the inter-electrode capacitance of the tube is part of
the tuned circuit.

I don't know if the poster was referring to it, but QST ran an article
in a December issue, I think 1972 but it might have been 1971, by someone
from Millen about their work on making a solid state version.

They used the same coil set and tuning capacitor, though I don't recall
if they changed the dial.

It was not a conversion article, not a construction article, but about
what they needed to do in order for the solid state version to put out
a flat output, with few false dips. It was interesting to read, at the
time.

Michael VE2BVW

"I don't know if the poster was referring to it, but QST ran an article in a
December issue, I think 1972 but it might have been 1971, by someone from
Millen about their work on making a solid state version."

You get a gold star on the memory test. It was December of 1972. I think
it was titled "Anatomy of a Grid Dip Meter", and it was written by the chief
engineer at Millen, who had led the conversion team. It is a worthwhile
read for anyone who thinks of converting an rf device to solid state. In
particular, the simple rf choke became a substantial barrier. The end
result was multiple rf chokes and ferrite beades placed in just the right
order to work at all frequencies. I recall Millen worked for days on the
"simple" task of creating something that would work as an rf choke on all
frequencies.

Colin K7FM



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