Pacific Radio News, June, 1921, page 368:

 
THE
CALIFORNIA
THEATRE
RADIOPHONE
(By  Lieut.  E.  W.  Stone)
 
California Theater radio room THE De Forest radiophone station operated at the Moorhead Laboratories, Inc., of that city, which is the exclusive distributor of the De Forest Company on the Pacific Coast, has been in operation for over a year and it is thought that a description of same will be found of interest to readers.
    The California Theatre is the largest motion picture house in San Francisco and is one of three controlled by the Famous Players-Lasky Corporation, the other two being the Imperial and Portola Theatres. A fourth, the Granada, in under process of construction.
    The station was installed early in 1920, through the courtesy of Directors Roth and Pardington of the "Big 3" Theatres, and is located in a concrete room in the fly galleries of the California Theatre. The antenna is rigged off the tower of the Humboldt Bank Building, directly adjoining the theatre.
    The transmitting set consists of the standard De Forest 1 KW radiophone set with additional loading inductance so as to obtain the working wave length of 1260 meters. The call letter of this station is 6XC. The antenna current varies from 4 to 5 amperes, according to the amount of input energy. Ordinarily, less than a half kilowatt is used for transmission. As the set is essentially an experimental one, various transmitting circuits of the De Forest Company have been tried out. The circuit at present in use is one developed by the engineers of the Moorhead Laboratories, for which patents have been applied. The receiving set is of the standard De Forest type.
    For best results in receiving from the California Theatre, the following Ultra Honeycomb Coils should be used: Primary--DL 200, with series condenser on moderate antenna. Secondary--DL 200, Tickler--DL 150.
    In connection with the transmission of music, several interesting methods have been developed through experimentation. For collecting and transmitting the music from the theatre's symphony orchestra of 50 pieces a large Magnavox horn is suspended in the fly galleries in such a position as to be clear of the side "drops." At the small end of the horn, a Kellogg microphone transmitter is mounted in a vertical position. From here the usual wires are lead to the radio modulating circuit. For the transmission of phonograph records, several devices have been used. One is a standard Magnavox phonograph microphone, consisting of a microphone mounted at the end of the usual phonograph tone-arm. Another method developed by the Moorhead Laboratories is to utilize the steel needle holder so as to bear directly on the microphone diaphragm in place of the usual phonograph diaphragm.
    For special concerts, which are frequently given, a sound-proof room in the basement of the theatre is utilized. For small chamber or instrumental music, a Magnavox horn similar to the one suspended in the fly galleries is utilized, but for vocal selections Kellogg desk transmitters are used by each singer. By placing the singers with their backs to the grand piano used for accompaniment, enough of the sound intensity from the piano is obtained through the singers microphones so as to obtain a proper blending of the voice and piano.
    Harp solos by Miss Jay Clark, piano solos by Mr. Hans Hanke, and vocal solos by Miss Mary White, Miss Ruth Williams, and Mr. Ford Rush of the California Theatre, and Madam Frieda Hempel and Forrest Lamont, stars of the Chicago Grand Opera Company, have been the big features of the special concerts.
    The regular concerts, consisting of the Herman Heller Orchestra music and phonograph records, are sent out at 4:00, 7:15 and 9:00 p. m. on weeks days, lasting for at least one-half hour. Special vocal and instrumental concerts are sent out at 9:00 p. m. on Wednesdays, and a special Sunday concert given by the Herman Heller Orchestra is sent out from 11:00 a. m. to noon.
    The transmission of music from the De Forest station at the California Theatre has developed from an experimental standpoint to a worth-while contribution to the musical progress of the city, and receiving sets for the reception of this music alone have been installed at clubs, hospitals, hotels, and many private homes since the inauguration of this service.
    The accompanying photograph shows Dr. Lee De Forest, inventor of the audion, at the radio set, and Miss Mary White singing over the set on the occasion of one of the special concerts. The station is operated under the direction of Lieut. Ellery W. Stone, general manager of the Moorhead Laboratories; Mr. B. F. McNamee, chief engineer, and Mr. I. E. Squires, operator of the station.