Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-09-27
Planes Electric
Shadow Sweeps
Path for Radio
c. Francis Jenkins Makes
Discovery Long Awaited
~ in AerOnautics.

An electric shadow" which extends
a searchlight beam behind, airplanes
may solve q problem which has dis
turbed aeronautical and radio engineers
for many years and which has cost
airplane manufacturers and operators
many thousands of dollars. it was an
nounced today by c. Francis jenkins.
Washington scientist and inventor. fol-
lowing tests yesterday afternoon.
For several years scientists have been
struggling with the problem Of over
coming electrical disturbances from the
ignition systems of airplane motors.
which formed one OF the chief Stum-
bling blocks in the way of radio COM
munication between airplanes and the
ground
Long and costly research work finally
led to the development of system Of
shielding" Of the high tension wires
of the ignition system to prevent radio
. interference. In connection with the
shielding 1t became necessary to bond
all the metal parts Of the airplane by
wiring them into single electrical unit.
Costly Operations.
Shieidins and bonding sre costly
operations. the expense, 1t is said. rum
ming as high as 81 700 for certain types
of planes Not only is the operation ex-
pensfye, but 1t has been the cause of
trouble and q source of danger to pilots
and passengers. Electric leaks" develop
in the shielding system and it is claimed
that the shielding is apt to cause short
circuits In the ignition system, result
ing in forced landings.
Shielding and bonding are done away
with In the jenkins device and per-
feet two.way radio communication Is
possible from any airplane, he claims.
Flying in an unshielded and unbonded
airplane of the standard commercial
production type, Mr.. Jenkins maintained
continuous Iwo-way radio-telephone
communication between the plane and
his Connecticut avenue laboratories
yesterday afternoon on a trip to Langley
Field, Hampton. Va. and return. Today
he was making another test flight to
Philadelphia.
been ridiculously simple" Mr.. jenkins
said. I'VE have found that there is
an electrical shadow behind an air
plane, spreading out like searchlight
beam, in which there is no interference
from the electrical high tension wires
of the; motor. - ~.--. -..
Towing In shadow"
ITO avoid interference it is necessary
only to tow the radio antenna in this
electrical shadow There is no need for
shielding or bonding. Perfect reception
and transmission are possible"
The antenna is made fast TO the top
of the airplane rudder or is reeled ont
from the fuselage through guide in
the rudder The antenna may he made
fast before the plane takes of end the
bare wire towed off the ground. Mr..
Jenkins said If a reel is used. small
wind cone or sock" is attached TO the
end of the antenna to draw the wire
out through the rudder.
The complete radio equipment used
on Yesterdays flight, Mr.. Jenkins said,
weighed but SO pounds. including bat
teries. The receiving and transmitting
apparatus and batteries were contained
in q single unit measuring II by Is by
4 inches. This unit was placed 0n one
of the seats in the plane, protected BY
a cushion. :
No wiring was necessary beyond plug
ging In the head. phones and antenna
and grounding the set on the metal
fuselaee." Mr., jenkins said. I'VE sop.
Grated on 47-meter wave length. one
of the five lengths aiiocated to US by
the Government. I There was no dim
Guilty in transmitting or receiving at
any time. On the way back from Lang
lev Field I asked one Of the men at the
Iabora tories to have my car driven to
washington Airport and when we
landed 1t was waiting there"
At Langley Field the installation was
examined by DR.. George w. Lewis, di-
rector of research OF the national adj
visory committee for aeronautics; Henry.
]. E. Reid, engineer in charge of the
Langley Memorial Laboratories, and
Mai. Walter II. Frank OF the Army
Air Corps Tactical School.