Evening star. [volume] (Washington, D.C.) 1854-1972, 1926-03-14
No. 56-Trying New Tubes.

Always looking for improvements
IN radio reception, it was not surpris
ing that Smith should take an active
interest in the new semipower tubes.
His activity in this connection, how
ever, turned out surprisingly for
when he had purchased power tube
picked at random from the large
stock offered by his favorite radio
store, he found that it didn't work.
For a time he emphatically was
"off" mower tubes. Then one day he
WAS treated to some particularly good
reception from new set employing
the new tubes. That revived his In
terest and soon led to the discovery
that tubes, like any other units OF
radio set. must be used in their proper
places.
1t developed that Smith had tried to
use the power tube in place OF one
OF the radio frequency tubes, but
without success. He had tried 1t IN
place of the detector tube. and stu
no success Even if he had used 1t
for the final stage of audio ampNn-
cation nothing would have happened,
because he was not making allowance
for the fact that these power TUBES
are designed to operate on higher
plate voltages and higher grid volt
age for blasting.
Overlooking Tubes.
Ii he had known something of the
difficulties presented by the ordinary
type of tube when used as an ampli
fer he would have come little near
CT to using the new tube properly.
The great difficulty with amplitier
tubes lies in overlooking them. This
is quite apt to be the case by reason
of the scant consideration given for
the grid blasting done with the aid OF
The &C. or grid battery. Knowing
little of this. Smith could not have
been expected TO realize that with the
new tube he could increase both plate
ana grid yoltages and enjoy better
loud speaker operation. provided his
loud speaker was suitable for the
conditions.
Here is where YOU want to avoid
common mistake / advised him.
Good radio reception with respect
to arrangement of units and their
selection is largely a matter of
matching or balance
1T is not so long ago when radio
fans had to change the tubes around
now and again TO match up the vari-
pus values and put the set in more
satisfactory working condition. Also
new tube were substituted, the
whole works might easily be thrown
out Of key. One reason for the great
Improvement in this connection is the
success of the tube manufacturers in
matching their products of equal
model. There is still some need for
matching tubes in multitude sets, but
usually this is done as IL matter of
obtaining super-results.
Nov. the minute YOU attempt to
use II tube that calls for higher plate
and grid yoltages YOU are upsetting
the balance, and if you want proper
results you must know what you are
doing. The big thing to recognize
In trying Semipower tubes is to use
them where they belong.
Semi-POwer Tubes.
Use semi-power tubes like C\-l12.
UE-2l0, U%-120 and CV-202, Clear
tron. Heliotron, Western Electric 216
A and the like for the second, or last.
sudio amplifier stage. That is where
they are intended to be used and is
The first point for YOU to remember.
THE next step is to know how such
tubes can give greater loud-speaker
volume. You may be surprised to
know that ordinary and semipower
tubes give about the same power re-
suits when operating under the same
conditions, and yok may wonder
what advantage the new tubes offer.
Note however, that / said under the
same conditions There is the key
note of the situation. The new tubes