[ARC5] Crystals Update

[Michael Tauson]

Ah, yes.  Progress.  It’s a wonderful thing.

Okay, so anyway … I now have a bunch of FT-241 & FT-243 crystal
holders (both wartime but with prewar parentage) as well as another
bunch of blanks to fit FT-243 holders.  Thanks to the good offices of
two of our number, I also have some mystery holders, specifically some
CR-4*/Us and a DC-10.  The CR-4*/U holders look like FT-241s but are
for something that operates in the frequency range of at least 70-90
MCs.  The DC-10 holder is about the size of an FT-241 but rather than
having pins it has two flat ears sticking out opposite sides that
appear to be intended for something like screw-type binding posts.
This one has a crystal for 4495 KCs.  If anyone has any idea what
these holders are for, I’d love to know what they are.  Oh, and the
multiplier train for the CR-4*/Us as well.  That would be nice.

A few holders I would like to have haven’t yet made an appearance,
holders like a few of the various round ones.   (Some of the squarish
ones are coming in next month.)  Being clever and outrageously
talented, I may have enough information to get creative with casting
resin and 3/32” brass sheet for some of them and some larger squarish
ones made using the ones inbound as masters.  While I’m casting I can
adapt them to the FT-243 blanks I have which would make things
terribly convenient.

Freepatentsonline.com is my friend and has been for a long time.  This
time, they coughed up a bodacious bunch of crystal holders and mounts
with publication dates from 1927 to 1945 (actually a bit later since
the applications were made during the war and the grants didn’t happen
until a few years after) with a few of them of high interest.  Among
other things I found some interesting holders that accepted the
crystals and pressure plates as replaceable units plus the patents for
the FT-171, FT-243 and a few others plus their predecessors.

Okay, so now … I have a couple of questions.  First, somewhere lost in
that echo chamber I laughingly call a mind is a dim memory of a way to
use a grid dip meter to check crystal activity.  The problem is I
can’t remember how it’s done.  Can anyone point me in the right
direction to finding this again?

Second, we all know that the thickness of a crystal has a direct
bearing on its frequency but lost in that same echo chamber is any
reference to the effects of changing the other two dimensions.  I
remember that latter becoming important in a few cases when I was
grinding crystals back when but I don’t remember why.  Again, an
assist in pointing me in the right direction would be gratefully
accepted.

Oh, and the asylum called to let me know my room is ready.  :-)

Best regards,

Michael, WH7HG
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