Measures for Progress: A History of the National Bureau of Standards

194 THE WAR YEARS (1917-19)
read," it was reprinted when Army and Navy schools and a number of
colleges later adopted it as a standard radio textbook.8°
From the beginning of hostilities, the Bureau and the military services
were bombarded with ideas for using radio as a weapon of war. Most
notable perhaps was Thomas Edison's proposal to establish a transmitting
station near Ostend, in British-held Flanders, to interfere with radio com-
munication between German submarines and their bases. The Bureau had
to tell him that a single station probably would not be sufficient. And even
if it were, interfering signals sent out from even that one station in Flanders
might well spread along the whole of the Western Front and confuse all radio
communication there.8'
A more practicable approach to the U-boat menace seemed possible
through Kolster's radio direction finder, still in the experimental stage when
we entered the war.82 With the incorporation of a French electron tube
amplifier and a new coil aerial, replacing the former antenna, a more com-
pact unit with greater range of usefulness at once became possible. It was
seen not only as an aid to air and sea navigation but as a potential means of
locating enemy radio sending apparatus and, therefore, the enemy himself,
whether in the trenches, in the air, or under the sea. Essentially a simple
rotating coil that detected transmitted radio waves and then narrowed down
the direction from which they were sent, the improved direction finder under
ideal conditions achieved a pinpointing accuracy of close to 1 percent.
One application of the radio direction finder, largely the work of
Kolster's technical assistants, Willoughby and Lowell, appeared particularly
significant. So far as was known, no navy had developed a radio system
for use in submarines, in the belief that sea water could not be penetrated
by radio waves.83 Before its first underwater tests, the Bureau had deter.
mined that with exceedingly sensitive amplifiers the coil aerial of the finder
might act as both a transmitting and receiving device. Next, the Bureau
began underwater tests of the coil and found, surprisingly, the signals almost
as strong as with the coil in the air. Experiments on cruising submarines
followed, and in final tests off New London in June 1918, the apparatus picked
80 See chap. III, p. 138. Southworth, Forty Years of Radio Research, pp. 36—38; "War
Work," pp. 227—229.
Still another Signal Corps publication prepared at the Bureau was Vacuum Tubes:
Theory and Use, a compilation of all available information on the subject for the use of
Army and Navy radio engineers. NBS Annual Report 1918, p. 47.
8tLetter, SWS to Thomas Edison, Dec. 7, 1917 (NBS Box 1O,.IEW).
82 The basic idea of the direction finder was an Italian invention, to which the British
secured rights in 1912. Kolster's invention appears to have been an independent discov-
ery and sufficiently different to raise no question of patent infringement. Schubert,
The Electric Word, pp. 139—140; conversation with Percival D. Lowell, Mar. 4, 1963.
82 War Work, p. 231.