A De Forest Transmitter at KRE
     


This is an excellent, highly detailed image showing the transmitter room of radio station KRE in Berkeley, Calif., about 1930. 

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 antenna.

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).

The 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 Electric.

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.

The 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 floor.

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 continuous broadcasting.

John Schneider is a lifelong radio history researcher. Write him at jschneid93@gmail.com.

This is one in a series of photo features from his collection. See past images under Columns/Roots of Radio at radioworld.com.


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