[Milsurplus] ARC-5 Receiver and other tube questions

[Mike Morrow]

Ray wrote:

>I always thought the metal case tubes were newer and better
>design then the glass tubes, the metal blocks inter electrode
>coupling, with a metal tube you don't need a separate tube shield.

GE's interesting patent for metal vacuum tube technology is available
at: http://www.freepatentsonline.com/2124428.pdf

Patent application was made in September 1934, and granted in July 1938.

Advantages claimed are ruggedness, and electromagnetic shielding.

>The old primitive BC-348 receivers used glass and shields where the
>newer series like the BC-348-Q used modern metal tubes not requiring
>exposed grid caps and tube shields.

Yes, but the main innovation in the BC-348-J, -N, and -Q appears to be
that they were significantly cheaper to build than earlier versions.
The circuit is simplified, such as elimination of the tuning capacitor
ganged potentiometer that altered stage gain as frequency was varied.

I guess cheaper is relative, since I read somewhere that the BC-348-Q
cost the government about $350 each.  That would be about $4000 in 2009
dollars.

I'll always consider the BC-348-R as the best of the lot, in spite of
many having those plastic nomenclature tags.

>The ARC-5 stuff never evolved into anything requiring a redesign
>like the BC-348 did...

I would loved it if GE had re-designed the BC-375-E to use something
more modern than the antique-by-WWII 1920s-vintage VT-25 (210) and
VT-4C (211) tubes.

I've matched a used BC-348-P, with the oldest tube lineup, to my BC-375-E
in the SCR-287-A.

I've matched a used BC-348-R, with a middle-era tube lineup, to my used
T-47A/ART-13 in the AN/ARC-8.

I've got a NOS BC-348-Q, but I keep it around for its external beauty,
looking as new and untouched-since-1945 condition as it does.  :-)

Mike / KK5F