This is an excellent, highly detailed image
showing the transmitter room of radio station KRE in Berkeley, Calif.,
KRE was operated by the First Congregational Church; this room was located in the
back of the church building. Two towers on the church property supported the
This is a de Forest 100-watt “radiophone”
transmitter. There are six RF tubes on the upper deck and six more modulator
tubes on the lower level (lots of glassware just to generate 100 watts).
nameplate indicates that this unit is Serial No. 101 (probably the first
production model) of the de Forest Radio Company of Passaic, N.J., and it lists
a long list of patent numbers covering the circuitry.
When commercial broadcasting began in the 1920s,
Western Electric held a patent monopoly on transmitter technology. When that
monopoly was finally broken in the late 1920s, a few other companies entered
the field, the principal being RCA.
De Forest had a number of marketable patents and
so it entered the market as a low-power, lower-cost supplier. Its principal
customers appear to have been the smaller independent broadcasters and police
and airport stations.
The two audio panels seen on the right were made
by Jenkins & Adair in Chicago, another company that provided equipment to
the smaller stations that couldn’t afford the prices of RCA or Western
A small manufacturer, Jenkins & Adair
specialized in audio systems for sound recording, motion pictures and
broadcasting. It merged into the Bendix Radio Company in 1936.
The audio panels contained the audio amplifiers
for line output and monitoring. The patch panels and amplifier volume controls
functioned in place of an audio console, which were not commonly used in 1930.
condenser microphone on the operator’s table is a Jenkins & Adair model
C-6. The preamplifier inside the microphone enclosure got its power from the
audio rack, which in turn took its filament voltage from the batteries seen on
The original print of this photo, by Roy A.
Williams, is in the archives of the California Historic Radio Society. The society
today occupies the 1930s KRE art deco studio building in Berkeley, which it
operates as a headquarters, meeting place and museum.
KRE is today known as KVTO(AM), operated by
Inner City Broadcasting Corp. as a Cantonese-language station.KVTO recently marked its 90th anniversary of
Schneider is a lifelong radio history researcher. Write him at email@example.com.
This is one in a
series of photo features from his collection. See past images under
Columns/Roots of Radio at radioworld.com.