[ARC5] W5SUM Discovers SCR-274N Mystery

[J Mcvey]

My guess is since it was for several different models, it may have originally been a 100 KHZ crystal for calibrating the dial tick marks?God only knows why the ham did what he did to it!
 

    On Friday, June 23, 2017 10:16 PM, Mark K3MSB <mark.k3msb at gmail.com> wrote:
 

 I wouldn't think professionals would build devices and label them only to drive a screw through said labeling as part of production.
I think the cap and screw were "aftermarket", but not necessarily by a ham.  Even today in our development and lab areas at work if we need a gizmo we make it with what's on hand.  Neccessity is the mother of invention.....
Mark K3MSB
On Jun 23, 2017 1:09 PM, "Michael Hanz" <aaf-radio-1 at aafradio.org> wrote:

I suspect we are seeing two things at work.  The first is a modification made by professionals, the second made by a ham who installed the button capacitor.  Note how he chipped the phenolic and drilled right through the nice engraving.  I am only speculating, but one possibility might be the Lockheed Aircraft Service 274N crystal modification introduced in 1947.  Drawing attached.  This drawing only mentions the BC-696-A and BC-458-A, but there would be no reason why it could not have been later expanded to all four 274N transmitter types.

I had to resample the drawing to get it under the attachment size for this reflector, but I'll send the original 3500 pixel wide drawing to anyone who wants it, or put it in the docs section of my aafradio webpage if there is enough interest.

         73,
 - Mike  KC4TOS

On 6/23/2017 11:47 AM, David Stinson wrote:

After all these years, I thought I had seen
everything one could see concerning SCR-274N,
but Ronnie, W5SUM, has discovered something
intriguing.
Ronnie acquired a ham-modded BC-696.
https://goo.gl/photos/2ScqwpTX rHxNT6ZY7
Rattling-around the inside was an interesting
artifact:  an FT-243 crystal holder with its face
and internals removed, a "button" capacitor installed inside and a WWII-era plastic "handle"
attached:
https://goo.gl/photos/fSKufUSF bpwogPD86

Things get interesting when you turn the crystal holder over:
https://goo.gl/photos/4cZDarBP GCT3Pjsp9
Engraved on the back:
FOR USE IN RADIO TRANS.
BC-457
BC-458
BC-459
BC-696

Were this some kind of  "calibration crystal"
for the eye tube which a ham gutted,
one would expect the Signal Corps to order them with markings for the corresponding transmitter to avoid confusion,
not for all of them.  The polymer used for
the "handle" seems much older than something
used by a 1950s ham and its decay matches
period materials.

Ronnie is kindly sending me the transmitter and
the artifact, hoping that he and I may be able to tell ham mods from any possible Signal Corps mods.

Any ideas or discussion on the possible use
of this surprising bit?



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