[Milsurplus] subminiature tubes question

[Mike Morrow]

I'm confused about what the original question was asking.  Was it asking for
a guess on the percentage of sub-mini tubes which have directly-heated vs.
indirectly-heated cathodes, or was it asking about the percentage of similar
tubes which used no filament, such as a gas regulator tube?


Most of the military gear designed from the early 1950s to the dawn of
practical transistor designs used indirectly heated sub-mini tubes.  I've
got a couple of UHF aircraft sets full of them (ARC-34, ARC-52, ARC-44,
ARC-45, ARC-48, etc.), and HF sets (ARC-38A, ARC-58, ARR-36, etc.).

>I think the URC-4 flyer's rescue radio also used mostly subminis. Maybe the
>later one, URC-10, also??

The URC-4 had directly-heated cathode sub-mini tubes except for the final
PA.  So did the 243.0 mc RT-285/URC-11, while the later RT-285A/URC-11 had
one of its tubes replaced by two transistors.  The same comment applies to
the VHF (121.5 mc) version of the URC-11, the  RT-350 and -350A/URC-14.
[Side comments:  (1)  I have never been able to find a manual for the
URC-11, which is odd considering how many of them there are out there.  (2)
The VHF version URC-14 was a standard *commercial* airline emergency set
used by US airlines into the mid-1960s, judging from a Pan Am radio shop
manual I've got. ]


The RT-278(*)/URC-10 was a later design than the AN/URC-11.  It was all
transistorized and used a superhetrodyne receiver rather than a regenerative
design.

>> Anybody out there with a proximity fuse collection care to comment ?
>
>Altho these have appeared from time to time for sale, it still amazes me
how
>thoroughly the stock of millions has been thinned down.


I'd love to have an inert WWII VT fuse in my collection.  I've never seen
one in real life.  There's interesting history at
http://www.history.navy.mil/faqs/faq96-1.htm, and a great cross-section
picture at http://www.history.navy.mil/pics/shell2.jpg .

>BTW, anyone know the frequency band these things worked in?

http://www.smecc.org/radio_proximity_fuzes.htm  notes 180 to 220 mc.

In a somewhat-related (to fuses, that is) area, one of my great regrets is
not making a copy we had at the Georgia Tech Naval ROTC library of the
*declassified* tech manual for the USN's WWII magnetic influence exploder
for its torpedos.  That unit turned out to be grossly undertested, thus
unreliable in combat, yet ultimately was greatly improved.  All I recall now
is that it used several metal octal tubes in its circuitry.  The obsolete
(since the mid-1970s) Mark 37 submarine homing torpedo, used, if I recall
correctly, sub-mini tubes in its sonar homing circuitry.

Another great regret I have is the loss of a small battery-powered portable
AM radio (about 7x4x2 inches) which used ALL sub-mini tubes inside.  I don't
even remember who made it.

73,
Mike / KK5F