New-York tribune., 1922-08-27
Can Power Be
Transmitted
BY Radio?
Noted Scientist States His
Reasons Why 1t Is Not
Possible With the Present
Apparatus for Radiation
Small Energy Received
Because Of Inability to Pre-
vent Dissipation by Radia-
ton on Reflected Waves

By DIR. Charles p. Steinmetz
The successful development of radio
communication by telegraph and tee
phone raises the question of.sthe possi
hility or impossibility of radio power
transmission.
In some respects radio power trans
mission exists to-day, for the message
which you receive by radio has been
carried by the power of the electro
magnetic wave from the sending to
the receiving station. However, while
the sending station sends out electro
magnetic waves of a power of several
kilowatts, or even hundreds Of kilo-
watts, this power scatters in all direc-
tions, and it may be only a fration of
a milliwatt with we receive; that is,
less than a millionth of the power sent
out.
The problem of power transmission
essential ydiffers from that of the
transmission for communication, that
in power transmission most, or at least
large part of the power sent out by
the generating station must arrive at
the receiving station to make it eco
nomical to transmit the power.
Directed Wave Necessary
Hence, the problem of radio power
radio waves so closely that large
part of their power remains together
SO as to be picked up by the receiving
station. Much successful work has
| been done in directing radio waves,
and for instance our transatlantic
/ stations send out most of their power,
| eastward. But still even as directed
the power scattcrs over the coasts of
| Europe from Norway to Spain, so that
it is impossible to pick up an appreci-
able part of it.
The limits of impossibility of con-
centrating beam Of ranio waves may
be illustrated by comparison with
! beam of light Light is an electro
radio wave merely by having wave
length many million times shorter
| While usually the light scatters in all
| directions, like the wireless wave, we
! can direct it in concentrated beam
| by the searchlight. But there is inev-
| itably scattering of the light in the
searchlight BEAM and when the beam
starts perhaps with square yard sec
tion, at the searchlight mirror, at ten
miles distance it has at the very best
scattered to a diameter of 1000 feet.
and at 100 miles distance the beams
cover a section of sixteen square
miles.
If it were a beam of radio power it
would thus require at 100 miles dis
tance a receiving station covering six
| teen square miles-about four miles
wide and, what is still more difficult,
four miles high-to pick up large
part Of the power The cause of this
scattering is twofold. First, the inevi-
table imperfections of any apparatus.
No matter" how perfect reflector,
/ there are slight impcrfections, and at
| 100 miles distance they seriously count.
perfect reflector. the beam OF light
would stay together only if the light
came from mathematical point
AS 1T must. however. come from a
small area, this causes an inevitable
scattering which at best gives an angle
of scattering Of about 2 degrees. This
is about 100 times as much rs would
be permissible to economically trans
nit power 100 miles by direct radio
beam.
Probability of Success Small
Thus the probability of power trans
mission by directed radio is very
small, except perhaps in very special
cases where the distances are mod
crate and the efficiency of transmission
of secondary Importance.
The second possibility of radio
power transmission least theoreti-
cally-is by resonant vibrations or
standing waves. Suppose we had
very large sending station sending out
electro magnetic waves, not of hun
dreds but of hundred thousands of
millions of kilowatts, and suppose we
could find wave length where the
absorption in the passage of the wave
through space is sufficiently small so
as to be negligible compared with the
amount of power. Assuming first there
were no receiving stations Then the
waves issuing from the sending station
would circle the globe and return to
the sending station, and if the wave
length is adjusted so that the return
wave comedies with the outgoing wave,
IL would return its power. and little |
power would be required from the
sending station to maintain such
system of high-power standing waves,
only enough to supply the losses-jusr !
as little power is required in an cleo
trlc wire transmission system, to
maintain the voltage wave as long as
no current is taken off.
:: suppose now we erect second sta
ton, tuned for the same wave lenett
as the sending station. 1t would res
onate with the standing electro-mag-
netle wave issuing from the sending
station, thereby stopping its passage by
absorbing its energy. 1t would, as we |
may say, punch a hole in the standing
wave aheet coming from the sending
station. Power would then flow into /
this hole; the sending station would
begin to send out additional power to
maintain the wave sheet, and this |
power would be received by the re-
ceiving station. Any receiving sta
ton of suitable design would then be
able to pick UP power from theN uni-
versal power supply carried by the /
standing wave sheet covering the
Garth Also several sending stations
may send out power These smay
either have different wave lengths
then would not interfere. and the re-
ceiving station could be tuned to re-
ceiye power from any of the general
ing stations. Or--what would be pref