Dave,
You're right. The crystal-lattice filters were the primary ham
use. But, I did use a 518 KHz unit for a simulated Slaby-Arco
alternator CW transmitter in a demo I built for our Museum
https://rtm.njarc.org/ to give
visitors a feel for what Sarnoff heard when Armstrong demo'ed his
regen receiver at our site (Marconi Belmar, NJ) in 1914.
VIDEO HERE.
73,
AL
On 1/11/2026 1:52 PM, Dave Merrill
wrote:
Aside from
the few frequencies around 455kHz that were adapted for
sideband filters, what utility did any of the FT-241s have
beyond their original military use?
--... ...-- Dave N9ZC
They
are spiffy-looking though. :-)
Wayne
WB4OGM
On Saturday, January 10, 2026 at 04:29:59 PM MST, John Vendely
<[email protected]>
wrote:
Back in the late 60s, Esse Radio in Indianapolis had bins full
of FT-241s for a dime each, and in those days, it was rare to
find a bad one. It's true that today, a good 50% of them have
failed. Some have obvious problems like detached or corroded
bond wires, whereas the quartz elements of others seem to have
mysteriously lost "activity". A few years ago a couple of us
decided to fire up the old SCR-508s and 608s. Just for a
laff, I tried opening some failed FT-241s, and if they were
mechanically intact, ultrasonically cleaned them. To my
surprise, some came back to life. Occasionally, you can still
find individual FT-241As in sealed foil bags, and these have a
much lower failure rate. In any case, other than for use in
the original radios, the FT-241 has essentially no utility
today.
The FT-241 was an unusually difficult crystal to produce,
requiring state of the art techniques. There were multiple
attempts at setting up second-source FT-241 manufacturers, but
none succeeded. Only its developer, Western Electric, was
ever able to mass produce FT-241s. An FT-241 production line
was built at ITT which showed some promise, but the war ended
before it produced usable crystals in quantity, and the effort
was terminated.
For the truly hard-core who really appreciate this stuff,
there's a very interesting and lengthy chapter with detailed
technical info on Western Electric's complex FT-241 production
process in the book "Quartz Crystals for Electrical Circuits"
by Heising.
73,
John K9WT
On 1/10/2026 3:41 PM, Hubert Miller wrote:
>
These FT-241 LF rocks have a fail rate somewhere between 40
and 70%. Seeing that myself, dissuaded me from keeping any of
them. I believe the only people who might want them are the
vehicle militaria collectors.
I have not myself seen any article on how to bring them back.
Maybe two tiny pressure point contacts, that might get some
resonant activity, but there's no longterm fix i know of.
The 'Boatanchors' ham radio group a decade or so back, had a
mass dispersal of an FT-241 lot someone had found. Known as
"The Great Crystal Caper". I was sobered by the miserable
results testing the crystals, and i wrote off keeping any of
those series.
-Hue Miller
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