Evening star., 1927-01-09
HIGH POWER LEVEL
IS ENGINEERS AIM
Present BroadcaSting Is
Based Upon Too Low Fig
ure, Report AscertainS.

Present radio broadcasting Is based
reliable, yearround radio reception to
listeners even within 10 to 20 miles
of station. according to recent
studies made by the engineers of the
American Telephone and Telegraph
Co. Consequently higher power ap-
preaching so kilowatts Is believed es-
sential for stations which serve many
distant listeners or which strive to
provide anything like Statewide or
national programs.
Field strengths, or the actual poten-
tial OK a radio wave received on q
set, should be of 10000 or more micro
volts to be desirable and free from
interference so as to insure reliable.
year-round reception, the report of
the telephone engineers, written by
Lloyd Espenschied, states. The dis
tance at which this requirement Is met.
OF course, depends upon the power Of
the transmitter. For example. the re.
liable range of q one-kilowatt trans
m1tter is between 10 and 20 miles.
depending upon the absorption of the
emitted signals; and the common 500
watt broadcaster is held entirely too
small to adequately serve large areas
A tWo-kilowatt station would increase
the reliable reception range by but
few miles, while a 5-kilowatt trans
mitter might cover a zone with a.
radius of 40 miles, and a 20-kilowatt
set circle with an 80-mile radius.
1t should be added that a field strength
OF One-tenth the desirable strength
might carry to about 80 miles from a.
nve-k1lowatt station and still be audi.
pie. although not reliable or salts
factory for music.
Crux Of Operators.
Unfortunately the increased range
goes up very slowly with the increase
OF power. Even If there were no ab-
sorptlon, the range Of a station would
Increase only as the square root OF
the increase in power To extend the
O,000-microvolt field, or desirable re-
ception strength, from Is to 80 miles
would require an increase in power
from kilowatts to 100 kilowatts.
This is. of course, discouraging to the
operators of broadcast stations who
buy their electric power or think Of
increasing their transmitted energy
by purchasing more powerful equip
ment SO as to reach out into other
land and gain new listeners.
In general this technical report
recommends that a station be rated
at least 5-kilowatt, If a community
lying 40 miles in any direction is to be
supplied with audible daily programs
regardless Of absorption. 1t is prob
able that ordinarily the programs
could be received up to about 100
miles and perhaps 500 occasionally
well enough to serve, but not with
the reliability desired by radio en-
gineers or critical listeners.
Increases Are Required.
Twenty and fifty kilowatt stations
are decidedly in order now, the report
continues, by broadcasters desiring to
insure good reception at greater dis
tances. Such increases in power win
be required, it is held, If the broad
casting art is to be advanced to meet
the higher standards Of the future.
No greater interference between
stations would be caused by higher
power, If the increase in power was
general among all stations. The inter
ference difficulty today arises only in
particular cases where one station
suddenly makes large increase in
power while the others remain at
their previous low-power levels, Mr..
Espenschied explains.
One Of the greatest difficulties en-
countered today IS due to the plural
ity Of broadcasting stations operat-
ing simultaneously in the same area.
which requires very high Selectiyity
value in receivers.