Evening star., 1925-01-11
FINDS RADIO FIELD
STRENGTH
Increase of Broadcasting
Stations Cited by Depart
ment of Commerce.
BY CARL III. BUTMAN


With 538 broadcasting stations,
$4,000 amateurs, $50 commercial and
$3.50 ship stations almost constantly
on the air, the Department of Com
merce field representatives point out
that the need for field strength meas
uring apparatus and wave meters is
essential If they are to keep stations
on their proper wave lengths and see
that they are not using excessive
power.
Most of the inspectors now have
meters so that they can measure the
transmitting waves of all stations,
correcting them when they are off
their wave lengths, but none of the
field workers who police the air
has equipment for measuring field
strength. This apparatus is used to
ascertain the intensity OF signals of
a transmitting station al dinerent
distances. 1t measures the strength OF
tho received signal, from which the
power OF the transmtter may be ap-
proximated. With such a piece OF
apparatus on a truck or automobile,
inspectors would listen in and
measure the average strength OF the
signal of a broadcasting station at a
distance of l mile, miles and IS
miles This would enable them to
determine whether 500 watts or a
thousand watts is necessary for Gov
ering a given territory.
U.es Only Dependable Equipment
The only dependable equipment of
this type known is that developed by the
American Telegraph and Telephone Co.
With using such apparatus mounted on
trucks, which would also carry portable
receiving sets, with loop antennas, de-
partmental inspectors could greatly IN
crease the efficiency of their work and
cover more territory.
1t is understood that the department
hopes to secure authority to purchase
at least four light trucks with full field
radio equipment during the coming year,
so as to speed up its work on detecting
offenders of aerial traffic laws, keep
stations in their allotted radio channels
and locate interference. Later on il is
hoped truck for each of the nine radio
supervisory districts can be secured.
The need for radio-equipped trucks or
automobiles by the radio inspectors is
indicated in a recent report OF some
radio field work in San Francisco by
Supervisor Dillon.
The location of outside interference.
sometimes called faults" Mr.. Dillon
points out, has been due almost entire
~ to the fact that the inspectors were
able to mount a receiving set and loop
on an autOInOplle anu trace tilc ililct-
ference from point to point until maxi
mum signals were heard in the close
proximity of the fault.
Inspectors MCGOWAN and LoveJoy
worked until midnight seeking the
origin Of interference reported by about
$50 fans in san Francisco recently. and
finally ran it to earth as defective
light fixture The defective light caused
interference in radio broadcasting
Of hnl K ~
miles. as the noises were carried to
various parts of the city on connecting
and parallel light and power lines. Some
cF the fans aided in tracing this trouble
some interference by lending their
autos, so that the inspectors could
travel about tracing the noises
Complain of interference"
During November the supervisors
rf the nine radio districts of the coun-
try received 3,944 complaints of inter
ference from fans and amateurs, not
including many protests over the
phone and in person, of which no
record was kept. The cases reported
covered many sources and forms OF
interference: the spark set on board
A ship transmitting off its wave
length; the broadcasting station emit
ting harrnonics and the amateur who
transmitted code during the silent
periods Practically every complaint
will have to be invest gated by a
field representative of the radio sec
tion of the Department OF Commerce
and in many instances an inspector
will have to travel far afield to locate
and remedy the trouble. Some OF
them, however, are probably due to
the carelessness of the fans in operat-
ing radiating receivers, but all cause
more work for the small force of the
department.
The supervisor in Atlanta reported
only 80 formal complaints, but added
that they came from 15 cities in his
territory. The Chicago district led
with 756 written complaints; san
Francisco reported $50; New York es-
timated zoo: Baltimore, sos: Seattle,
500; Detroit, 312; Boston. 306 tbroad-
casters and the press reporting about
6oo); New Orleans, 50, and Atlanta. 80.
lis believed that all told, about 5000
a,mpiaines were received, including
phone and other protests.