The Washington times. [volume] (Washington [D.C.]) 1902-1939, 1925-11-18
IN PREFERENCE.
ON RADIO GAN
Be TRACED.
Examine Switch in House
Meter to Find # Trouble
Is Inside
By ROBERT 5. THORNBURGH

BY ROBERT s. THORNBURGH
OF first Importance to the radio
amateur suffering from interference
obviously from electrical apparatus
is survey of the situation to de.
termine the source Of his Difficult
ties.
Begin by making certain the dis.
turDance is not in the receiving set
itself, is the advice of Doctor ]. HI.
DelIinger, radio expert OF the United
States Bureau Of Standards.
Next open the electric switch at
the house meter the bureau scien-
fist said. If the interfering noise
is still heard in the radio set the
source is then known to be outside
az 1T Is then desirable to report the
situation to the electric power com
pany. Many Of the companies have
apparatus for the purpose OF follow.
ing up complaints Of this kind.
How to Find Direction
Usually a sensitive receiving SET
with a coil antenna Is used to de.
termine the direction from which
the interfering noise comes and this
outfit is taken from place to place
until the source is found.
"The location Of such sources il
often very difficult and bathing
undertaking. The trouble sometimes
comes from spark discharge over
q pair OF wires or It may be that
the wire is touching some object
such as tree, pole or guy wire.
such a spark discharge 10 9
loss of power to the operating com
pany and a potential source OF Sc
riolls trouble, and for these reasons
the company probably is more In.
terested in finding and eliminating
this type Of leak than in finding
the radio receivers difficulty. Large
leaks and sparks may often be OBJ
served at night especially in hot
weather. However, sparks that are
too small to be noticed readily may
cause serious Interference with radio
reception
Direct-ourrent m6tors often cause
trouble with radio reception when
in operation near the receiving set,
especially when the brushes on the
motor are sparkling badly. the
parking, officials said, should Dt
reduced as much as possible by
cleaning the comTnItator and proper
setting of the brushes.
Find Rural Trouble
The remaining interference il
sometimes overcome by placing two
condensers about two rnicrofarads
each) in series across the power sup
ply line and connecting their mid.
point to q good ground system.
Another source OF interference
the Bureau OF Standards found, 4
the ringing machine used In rural
telephone exchanges. The elimina
ton Of this interference IL espe
ciaily important to farmers. Tele
phone engineers 1t was pointed out
can eliminate or at least reduce this
trouble by connecting a filter be
tween the machine and the ringing
keys.
Many cases Of radio interference
have been caused by electrical pre-
cipitatora which are used to prevent
smoke and noxious fumes on ma
terfal from leaving q chimney.
The precipitation operates by es
tablishing a highly-charged, electric
field inside the chimney OF such q
nature and direction that particles
going up the chimney are charged
and driven against the walls where
they stick,
To Prevent interference Here
Precipitators cause interference
for the reason that the high voltage
used in their operation is obtained
from a rectifier which produces
sparks and generates radio-frequency
alternating current as well as the
direct current which the precipitation
uses.
II the precipitator IL 30 designed
and arranged that the distance be
tween the rectifier and the chimney
is only few feet or IL the entire
apparatus including all leads IL
housed in a metal building there IL
usually no trouble