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

286 THE TIDE OF COMMERCE AND INDUSTRY (2920-30)
its work on the radio direction beacon, ground-to-air radiotelephony, and
develop a marker beacon system both to guide and track planes in flight.190
If the recent war saw the development of specialization in planes,
better planes and engines, sturdier airframes, wind tunnel research, and
aerial photography, postwar spurs to aviation were to include the experience
gained in flying the U.S. mails and inventions like the radio beacon, radio
compass, gyroscopic automatic pilot, streamlining, development of the mono-
plane, and of retractable gear. The glamor of the dirigible was only to be
exceeded by the headline performances of the planes that crisscrossed the
skies in the decade that began with Lindbergh's flight to Paris.
"POLICING THE ETHER"
The cross-licensing agreements of General Electric, Western Electric,
and Westinghouse in 1920—21, involving some 1,200 radio patents, ended
the long patent war in radio. For the first time since its discovery in 1907
the three-element vacuum tube was free from danger of infringement and
could be manufactured and sold to the general public. It was exempt from
Government monopoly, and there were no taxes on receiving sets, as in Europe
The radio boom was on.
In 1920 Westinghouse's experimental station KDKA at Pittsburgb
made history by broadcasting the election returns to a radio audience esti-
mated at less than a thousand. By the end of the first year of the patent
peace there were 508 broadcasting stations in the United States for the hordes
of crystal set and vacuum tube enthusiasts. The great radio craze really
began after Armstrong's superheterodyne, with its superior reception, came
out in 1922.191 Whereas in 1921 there were probably not more than 7,000
privately owned sets in the Nation, by 1928 there were nearly 10 million, not
counting home-made sets.192
As much as anyone, the Bureau fired up a nation of do-it-yourself
addicts by issuing a series of mimeographed letter circulars in the spring of
1922 on how to construct a simple crystal detector set for $10; a two
100 NBS Annual Report 1927, p. 40. See below, pp. 295, 297.
191 Armstrong's modification in the heterodyne introduced another oscillation with the
incoming high frequency signal which produced a third "beat frequency." This lower
intermediate frequency could be amplified much more effectively, permitting very high
selectivity of the original signal.
The Electric Word, pp. 212—214.
Not to be outdone by the Bureau's radio engineers, Clarence A. Briggs of the gage
section built a crystal set with coils on cardboard that, except for the antenna and
telephone receiver piece, cost 60 cents, and on which, without amplification, he picked
up Schenectady, 300 miles away. Letter, H. G. Boutell to Assistant to Sercetary of
Commerce, May 23, 1922 (NBS Box 21, PAC).