Evening star. [volume] (Washington, D.C.) 1854-1972, 1924-11-16
EXPERT SEES CUT
IN INTERFERENCE
Dr., J. H. Del|inger Says Fans
Are Learning to Avoid
This Handicap.

Interference. which has kept many
rotential fans from accepting radio
.eriously, gradually is being eliminated.
recording to Or. J. II. Deilinger OF the
bureau OF Standards. Fans who suffer
rom local interference have learned
now TO avoid II by using selectve re-
"eiving set. short aerial instead of a
long one, loop antenna, when the de-
sign OF the receiver permits. or hooking
IN OF wave trap. On the other hand.
there are still some listeners-in SO be-
hind the times as to wonder why they
cannot separate two broadcasting sta
tons when they have nothing but
liked crystal set Washington broadcast
listeners whose crystal sets were
equipped with a simple tuner found
little difficulty In getting either wRC
or "CAP during the recent simu!ta-
feous tests on separate wave lengths
Obviously, the development Of the radio
art. In broadcasting at least. is not
solely IN to the engineers. il Is depend
mt TO q considerable extent on the fans
themselves, who must keep posted on
developments and make their sets as
elective as possible.
There Is no simple cure-all for radio
interference DR.. Dellinger declares
Both natural and mammals interfer-
NICE" must be COPIED with. and the for
come. Nevertheless. this radio research
yorker is confident that the ether
gradually will be cleared OF impedi-
-nents or that these difficulties will be
overcome by scientific progress, and
mat radio will go on developing TO
new tr1umphs and greater service" DR.
oeihnser points out that interference
trises from many causes. Vast effort is
ie'hs made to analyze these causes and
n IA I'll
sion he said. in part:
Tuning improvement ut Peak.
The radio apparatus first used pro-
fnced waves OF very broad tuning. so
THAT II was very difficult TO tune out
other waves. Improvement in tuning
Nas gone steadily on. until we have
no" about reached the limit OF i'm
prove1nant In that tiirection-a fact
which is not commonly realized.
lhere are also other sources OF In
reference, in the reduction Of which
we are fast approaching the limit at
talnable. One is atmospheric electri-
cal disturbances, both natural and
artificial, which always exist if
Greater or less intensity and are par
'icularly troublesome In the Summer
and in certain places. The radio
public Is going to have to learn to
distinguish between removable inter-
ference and inevitable interference.
Science will find ways to circumvent
those sources Of interference which
science cannot remove. The slight
electrical discharges always going on
n the atmosphere, similar to very
tiny lightning discharges. cause a
certain background OF noise in a
radio receiving set, and these dis
charges can probably never be pre-
vented any more than variations of
he
sort of natural limit to what a re-
ceiving set can do, for II the waves
from distant station are weaker
than the average of these atmospheric
disturbances, no increase OF amplifi-
cation in the receiving set can bring
In the distant station without the In
reference.
Limits to Distance.
For the growing radio public
which demands real service and quail
tty in the radio programs. this situa-
ion means that there are definite
limits to the distance from a broad
last station at which satisfactory re-
ception is possible. To Increase that
distance, higher power must be used
II tho broadcasting stations. This Is
now recognised, and there will be
increases in the power of many Of
the stations. Considerable fear had
been expressed that the use OF high
power, while OF obvious benefit to the
warmers and others remote from the
stations, would make 1t harder for
city dWellers to tune out the nearest
stations when they wished to receive
others. This fear will not be realised
If the stations of higher and higher
power are located farther and farther
away from centers OF population. Re
ception conditions then will be bet
ter for city jewellers than at present.
when the principal stations are To-
Gated In the very midst of the cities.
ITO deal effectively with the vari
Gus sources of interference, 1t is I'M
portant that there be exact knowl-
edge of their prevalence. Some in
formation of this kind is available
as result of observation carried
on by the Bureau of Standards dur
ing the past two years with the CO.
operation of about zoo voluntary OBJ
servers. located up to 400 miles from
two selected broadcasting stations.
Preliminary results show the follow
ing averages for all observers: First
no interference, 90 per cent of the
times when reception was attempt
ed; interference from other broad
cast stations, so per cent; atmospheric
disturbances, IS per cent; fading or
irregular variation OF intensity Of
received signal, l3 per cent: amateur
.ranemftting stations, 8 per cent;
radiatins receiving sets, 5 per cent;
commercial radio telegraph stations,
, per cent, and non-radio electrical
interference, / per cent. More com.
plete results will show decreases IN
the percentages for the causes under
the control of man. and correspond
ing increases IN the percentages from
atmospheric disturbances and fading
Tho rnan-rnade interference OF the
various types is of local character.
some types of it being confined TO
very small areas around the source.
Interference to BE Cut.
The source OF largest Interference,
that from other broadcast stations,
will soon be still further reduced as
a result OF the new assignments Of
wave lengths made by the confer.
ence. The broadcasting stations are
distributed through somewhat
wider range of frequencies, and the
removal OF ship radio communications
from TIE broadcast range. Broadcast
station In different localities are
kept d om interfering by working on
different frequencies. Some inter-
ferenq results from slight variations
from the assigned frequencies, but
there Is marked Improvement in the
accuracy with which these fire.
"Interference from amateurs and
CONNIE rcial radio telegraph stations
has been steadily decreasing, partly
becsaus Sc OF: closer attention to stay.
ing within the assigned freQuencies,
and partly because OF rapidly increas-
ineiuse of the continuous-wave sys-
,an,. which produces much less inter-