[ARC5] W5SUM Discovers SCR-274N Mystery

[Michael Hanz]

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/2ScqwpTXrHxNT6ZY7
> 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/fSKufUSFbpwogPD86
>
> Things get interesting when you turn the crystal holder over:
> https://goo.gl/photos/4cZDarBPGCT3Pjsp9
> 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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