Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-11-17
FUTURE FORECAST
FOR BATTERY SETS
Advantage Seen for Owners
With Alternating Current
Not Available in Homes.
BY JOHN MARSHAM.

Most of the development work on re-
ceivinE set design during the last few
years .has had to do with increased
poveri with better tone quality, along
with improvements and Simplification
in turning. With this increased power,
coming as 1t does with the advent of
the successful socket-power set. has also
come the solution of the problem of how
to apply this added power without over
loading the vacuum valves and the loud
speaker. But there is another problem
of interest to a large number of lis
teners scattered throughout the coun-
try-how to get adequate power from
the battery set and the double-current
socket power receiver. This is eSpe-
cially true for listeners who live in rural
districts, or even in city dwellings where
there is no alternating current line.
Here in the United States We are as
extravagant in our radio work as We
are in OUR railways, automobiles, fuel
consumption and other items. We en-
ploy a great deal to obtain relatively
little. And so with radio. Many of our
present-day socket-power radio sets with
outputs of the order of $500 to $4,000
milliwatts, are capable of far more work
than We actually require. Indeed, much
of the energy is wasted as it is through
inefficient design, which is perhaps for
European Sets Conserve Power.
In Europe it is different. There the
radio sets for the greater part are oper-
ating on batteries, and the outputs are
relatively modest. Yet amazing tone
quality and volume are obtained, due to
extreme conservation of energy. Per-
haps the utmost in tone and volume is
obtained for the present status Of the
radio art, so that the results often
match those of American sets using
many times as much energy. With an
output Of so to 40 milliwattS, which is
equivalent to that of battery set with
a low power output tube, or, again, an
output of 500 milliwatts. which is fair
for power valve of the fila type
working within its distortionless limit,
ample valume and tone are obtained.
Queer enough the true bottleneck of
battery operated sets has been quite
overlooked all these years. While radio
experts and laymen have worked on
radio frequency amplifiers and detec-
tors and audio amplifiers in search of
greater volume and better tone, the
loud speaker has been accepted as it
stood. Yet the real beginning of eff
cient battery operation is the loud
speaker. The set can be no better than
its loud speaker, so that is the starting
point.
Types Of Speakers.
And what have we in the way of loud
speakers? There is the magnetic type,
which has hitherto been employed for
battery operated radio sets. Yet this
type Is relatively inefficient. If it is
made quite sensitive, it is necessary to
have the pole pieces quite close to the
balanced armature, and the latter men,
Der must be stif1y tensioned in place
to prevent pole slap. This stiffness i'm
mediately cuts off the lower frequencies
in the response, so that bass notes and
tonal depth are entirely missing Again,
if sufficient spacing is employed between
pole pieces and armature, the device is
insensitive and no considerable volume
Is obtained.
The dynamic type of loud speaker
combines In a most happy fashion the
desired volume and tone quality, but
requires far more input than is avail
able with battery operation. Hence 1t
Is out of the running
Recently. however. with the intro