Evening star., 1935-04-14

so lar no 0tner radio manufacturer
has announced his intention of adopt
ing the new types of tubes, which
measure only l to 8 inches above
the base and thus are considerably
smaller than glass tubes. Although
the RCA Raditron Co., leading Amer
lean patent holder and licensor of tube
manufacture, will produce the tubes
for the General Electric Co., the other
manufacturers, including the RCA it
self, seem to be taking the attitude OF
watching and waiting for the actual
everyday performance of the new
tubes before venturing to redesign their
radios to include them.
The all-metal tube Is not entirely a
new device. for the "catkin'' made its
appearance in England several years
ago, and engineers are still at vari-
Ance over its superiority. Unlike the
British metal tube, which is octagonal
in shape and can be used interchange
ably with glass tubes, the American
styles have eight prongs and therefore
cannot be interchanged with the four
to seven-pronged glass tubes. This
means that the receiving set must be
specially designed to accommodate the
metal tubes.
The American metal tubes are cylin-
drical in shape, some with reduced
diameters at the top. It is claimed
for them that they offer improved elec-
trical characteristics over the familiar
glass tubes For one thing the metal
shells provide their own shielding
against eXtraneous noises and inter-
ference and are shockproof. which
should make them particularly valu.
able for automobile and airplane
radios. This also renders unnecessary
the use of extra metal cans around
the glass bulbs.
Then, it is claimed, the metal shell
Is better heat conductor and radiator
than glass, much stronger and not
subject to breakage. thus insuring
longer life. In three-element tubes
the metal envelope itself can be used
As the plate, and in the four element
screen grids the shell is used as the
screen. Thus the metallic plate and
the screen mesh in the ordinary glass
tubes are eliminated. The short lead
wires permit greater amplifcation at
the higher frequencies, each lead-in
wire passing through a tiny bead OF
special glass that Is fused securely in
an alloy, which in turn Is welded to
the metal container to insure a long
life vacuum.
Although IL is said that mass pro-
duction can make the all-metal tubes
cheaper than glass tubes, they prob
ably will be somewhat more expen-
sive at the outset. Their small size
may also conduce to the production
of even smaller chasses and make
smaller cabinets possible, although it
is difficult to envision further dimin-
utiion in size from the midget and
"cigar-box" model radios still so popu-
lar on the market.
The new tubes presumably are
available to all of the IS or more
radio equipment manufacturers Ii
censed to employ RCA patents, RCA
being in turn licensed to use and
relicense most of General Electric S
radio patents. At least one of RCA's
major licensees, the Philco Company
of Philadelphia, remains skeptical.
however, for when the new tube was
announced Philco's engineering chief,
Walter E. Holland, issued the follow
ing statements through the trade press
while to the public a strong warning
Of caution was sent out:
when our research laboratories and
scientific tests indicate that all-metal