Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-12-22
Behind the Microphone
BY THE RADIO EDITOR.

possible.
Probably the most important,
and that which should be given
the greatest of care, is the inSer-
ton of the vacuum tubes. While
this may appear simple, confu-
sion of the tubes by placing them
in the wrong socket may do con-
siderable damage. The detector
tube and the Screen-grid valves,
of course, are not easily confused,
because of their five-prong base.
Even if these two kinds of tubes
were confused, however, while no
damage would result, the set
would not function properly. It
is also possible to confuse the
rectifier with one of the amplifier
tubes, in which case the f1lament
might be burned out.
However, in practically all re-
ceivers on the market today the
sockets are clearly marked with
the type number of the tube re-
quired. A corresponding number
is on the base of the tube. If
these numbers are watched care
fully there will be no difficulty.
Probably the most important
and helpful to the new listeners
is the method Of operation. This
information is usually supplied in
the form of an instruction book
with the receiver. The modern
set has only three controls-a
tuning dial, volume control and
an on-and-off switch.
However, with the inception of
the Screen-grid radio receiver
during tina last year a new con-
troll is frequently found on the
front panel. This is so-called
distance" and local switch.
It's purpose is to facilitate the re-
duction of the volume on the
local stations in order to prevent
distortion through the overload
ing of the detector tube. It
should always be set on local"
while listening to stations within
approximately so miles of the set.
This will insure the highest de-
gree of Selectivity and quality on
the more nearly located broad
casters.
Tuning the new radio receiver
is, of course, a simple procedure.
However, to locate desired sta
tions without some knowledge of
their relative position the dial
makes tuning difficult to the new
listener. Modern receiver dialS
are usually calibrated in either
kilocycleS or wave length. How
ever, the former designation is
more or less standard on the
latest types of sets. This is help
full in that it literally spots the
stations on the dial. Programs
published in newspapers usually
give the station, it's wave length
and frequency in kilocycles. Ref
erence to these charts tells the
frequency of the station and, by
comparison, enable the listener to
locate the station without diff
Guilty. 1t will be noticed that the
lower kilocycle stations will be
found at the maximum dial set
tingS.
Erection of an efficient aerial
is important to the successful op-
Grafton of the receiver. Because
OF the extreme SenSitivity and Sc
lectivity of the modern screen
grid receiver only small aerial
is required. In general they are
classified into three groups,
namely, indoor, outdoor and loop
antenna.
! For the most reliable all
around reception, including dis
lance as we'll as local, the outdoor
aerial is best. A well insulated
wire between rs and 80 feet long,
including the lead-in, is ample
for the modern receiver. Longer
wires are likely to give too much
pickup, causing poor Selectivity.
resulting in interference from
stations operating on adjacent
wave lengths.
In order to function at it's best,
only the highest grade of mate
rails should be used in the con-
Struction Of the outdoor aerial.
For the wire, enamel coated cop
per wire, supported with glass
lnSulatorS, is the best.
For the listener who does not
desire to use an outdoor antenna,
and is to be contented with local
and medium distance stations,
the indoor aerial will suffice. It
is, of course, the easiest to install.
With a modern sensitive set, a
wire between Is and Is feet
strung about the holding of the
room will give reliable reception
Of local stations. The loop aerial
should be used only with receivers
which are supplied with this type
of antenna. They usually consist
of several turns of wire wound on
a rigid form. Sets operating from
such antenna must be sensitive in
order to give good results, and for
this reason should be used only
with those designed to operate
from the loop.
Another important factor in the
successful operation of the new
radio receiver is the ground con-
nection. For ordinary receiving
purposes in the average home the
cold-water pipe will give excellent
results. A ground should always
be used with the electric set.
While it may be found that good
results may be obtained without
it, it's use will have the tendency
to eliminate any hum which
might filter through the ap-
paratus.
Where a water pipe is not avail
able a radiator may be used and
will usually give results compar-
able to those obtained when
water pipe is employed. A gas
pipe, however, should never be
used. because of its poor conduc-
tivity.
Location of the receiver in the
home frequently has an impor-
tant bearing on the quality of