Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-06-20
EXPERT EXPLAINS
SCREEN GRID TUBE
0. q. Caldwell Says Device In
creases Amplifcation and Sen.
sitiveness in Set.

What is this screen-grid tube, about
which so much ado was made at the
Chicago radio show last week? Do the
newly-designed radio receiving sets,
which were the cynosure of all eyes at
Chicago, represent a radical improve
ment over old types of receivers simply
because they employ Screen-grid?
These questions are being asked every
where by radio fans, particularly those
about to purchase new sets.
o. H. Caldwell, former member of
the Federal Radio Commission, now
publisher of several electrical journals
and himself an engineer of standing,
was asked to make reply. He thus ex-
tube, whose thinly woven mesh or
screen Of wire separates one tube ele-
ment from the other to make 1t posi-
bic to attain increased amplification and
greater sensitivity in the new sets.
THE Screen-grid alternating current
tube" said Mr.. Caldwell, marks a ire
men1ous technical advance in tube de-
sign in the matter of amplification and
sensitivenesS of operation. On that all
engineering advice seems to agree.
Increases AmpIification.
1.-THE outstanding characteristic of the
greatly increases amplification in both
radio and audio frequency stages. This,
together with its use as a power detec-
tor, gives increased distance reception
and added quality of reproduction.
From the electrical standpoint, it is
important to note that the screen grid
tube remains unaffected by small line
voltage changes. Due to the higher
amplihcation possibilities of this tube,
an extremely sensitive set also can be
designed, because of the sceren-grid.
The tube has characteristics which
eliminate the necessity for certain bal
ancing or neutralizing practices which
heretofore have been commonplace"
The screen-grid is said to be the first
major engineering change in radio that
has reduced rather than increased the
cost of manufacture. Since competi-
ton Is keen in this young industry, the
reduced cost Of making the set will in
evitably be passed on to the buyer. The
consumer also enjoys lower power-sup-
ply cost and maintenance expense.
Many of the set manufacturers are
turning to screen-grid designs exclu-
sively, and the tube makers say they
will produce large quantities of the new
tubes this year.
Screen Grid Has Critics.
The screen-grid has its critics as we'll
Certain manufacturers express cynicism
at the whole screen-grid situation, say
ing they will continue producing their
old lines until the future of screen-grid
demand is definitely known. 1t is a
fact that the unframed ear has diff
Guilty in detecting the difference in the
quality of the old sets and the new.
But the technical arguments all seem
to be in favor of the new.
Against the Screen-grid it is argued
that its present popularity is only a
passing fad stimulated by much ad-
vertising. Great sensitiveness is not
needed it is said. Screen-grids are no
better than any good commercial old
line set and will take their places merely
as another line to sell, according to
some observers. Moreover shortage of
tube supply is foreseen.
Nevertheless. the engineers are in
siStent that the screen-grid has come
TO stay.
tube" says Mr. Caldwell, must be re-
garded not only as a technical achieve
ment, making for better radio reception
but its advocates look to it as the first
triumph of economic improvements
device making better radio receivers less
expensive to build. If it can accomplish
this end, and also clear itself creditably
of the charges and complaints which
its critics have brought against it, the
industry will have taken long step
ahead and the "screen-grid era" will
be with us"
(Copyright, 1929. by the North American
Newspaper Alllance.D