OCR Interpretation


Evening star. [volume] (Washington, D.C.) 1854-1972, April 02, 1950, Image 130

Image and text provided by Library of Congress, Washington, DC

Persistent link: https://chroniclingamerica.loc.gov/lccn/sn83045462/1950-04-02/ed-1/seq-130/

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Interference tests on color television ore run by W. K. Roberts (right), assistant chief of the FCC laboratory, and F. D. Craig, radio engineer.
John E. Knight sets controls on a diathermy machine
being tested. The light bulb held by Rodio Engineer A. G.
Craig, although not connected to the drum of the machine,
is lighted by radio waves emanating from it.
Earl D Ball, electronics engineer, calibrates a signal
Generator < ieft», part of the equipment used by FCC field
^,cn Star Staff Photos by Elwood Baker.
Silencing' the Radio
THAT diathermy machine
your doctor uses for your
aching back can be a pain in
the neck to radio listeners.
And even that radar range
you’ve installed in your super
modern kitchen can knock
your neighbor's television gal
ley west.
These are samples of the
tid-bits one gleans from a
few hours in the technolog
ically rarified atmosphere of
the Federal Communications
Commission Laboratory at
Laurel. Md.
That laboratory is housed
in a small brick building atop
a knoll 4 miles northwest of
Laurel—a clay pot amidst
flowering antennae.
Here a small group of radio
and television technicians
make studies designed to keep
the air traffic in neat and
well-defined avenues. If it
weren't largely for their re
search the log-jam in the
ether would have radio lis
teners thinking they’d tuned
into a lion-jaguar fight with
a horde of banshees at ring
side.
Interference with your ra
dio and television reception is
their main concern. They ap
proach the problem by testing
sending and receiving equip
ment before it gets on the
market. It’s easier to do that
than to try to look into each
case of interference after
By Stanley Baitz
faulty equipment has been*
released to the public.
Their tests also help the
commission in allocating fre
quency bands to broadcasters;
they indicate how close to
gether stations might be
placed without the listener
receiving several stations at
once.
Now television interference
problems are beginning to be
set the researchers. They’ve
found, for - example, that
starting automobiles raise hob
with receivers, so they’ve be
gun to make overtures to car
manufacturers to cut down
on ignition potency.
Then there’s something
called “oscillator radiation.”
It’s best explained this way:
All radio and television sets
transmit as well as receive
signals. This fact, little known
to the non-technician home
user, has begun to give tele
vision owners trouble in cer
tain areas because of spacing
of the channels. For exam
ple, in Laurel, where it is par
ticularly bad, if one tunes in
on WMAL-TV in Washington
he gets the program all right,
but his receiver also gives off
a signal that raises ned with
the reception of a neighbor
who is tuned into a television
station in Baltimore. And
vice versa. It seems that tele
vision pictures are particular
ly susceptible to these signals,
much more so than regular
radio. The spacing of chan
nels here is such that the
problem does not confront
Washingtonians to any great
degree.
The FCC lab men have to
try to figure out some stand
ards for receiving equipment
that will eliminate this nui
sance.
Some of the things they
look into get rather far away
from the conventional idea
of radio—such things as dia
thermy machines, neon signs,
welding equipment and radio
cookers. Radio frequency used
for industrial, medical and
scientific purposes has ex
panded so much in recent
years that the total kilowatts
of equipment exceeds the to
tal transmitter kilowatt power
used for radio communica
tion. A startling statement,
but the FCC says it’s so.
Such equipment employs
the same frequencies used by
the communications Industry,
and if it is not properly de
signed and operated it will
emit severe interfering sig
nals. So the lab men have to
test the equipment before
manufacturers put it on the
market in order to make sure
it doesn’t operate outside the
band and foul up other traf
fic on the air.

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