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

290 THE TIDE OF COMMERCE AND INDUSTRY (1920-30)
The phonograph playing into the high-power radiotelephone transmitter may be the
experimental "broadcast station" pioneered by the Bureau. The date of the photo-
graph is September 1920.
Department of Agriculture, it pioneered an experimental radio market and
crop report service. Even before that the Bureau had successfully trans-
mitted music and speech for short distances over its station, but—such was
the novelty of broadcasting—for the sake of reliability the Bureau resorted
to Morse telegraph for the market reports. After operating the service for
1 months, the Bureau turned it over to the Post Office, whose stations already
served the air mail.203
It was not transmission but reception that harbored the real gremlins
of radio communication. The first of the technical difficulties that came to
the Bureau as commercial broadcasting began was that of fading or varia-
tions in the intensity of received signals. A statistical study conducted by
the Bureau traced still other forms of interference to their source in amateur
equipment, radiating receiving sets, and powerlines, arc lights and other non-
radio electrical equipment.204 Although queries about fading and noise
began arriving at the Bureau in 1921, little was done about them at the time
because of the even greater obstacle to reception, the interference between
stations in the overcrowded air.
203 NBS Annual Report 1921, p. 69; letters, SWS to Secretary of Agriculture, May 17
and Sept. 7, 1921 (NBS Box 10, JEW).
Dellinger and Whittemore, "Radio signal fading phenomena," J. Wash. Acad. Sci.
11, 245 (1921) ; LC182, "Electrical interference with radio reception" (September
1925).