Partial image of a 1910 era coast station operating position.

Antenna Change Over Switch

   Obviously in the normal course of station operation there must be some way of changing over from listening to the dits and dahs of the Morse messages in the headphones, to firing up the station's transmitter and answer the calling station. In the photo above this change over from receive to transmit was accomplished by the switch shown in the middle of the photo, its handle presently in a vertical (receive) position. The handle, being hinged at its base, would rotate 90 degrees forward and down to enable transmission.

   A similar switch from the 1910 period is shown on the right. In the top image A is the Bakelite handle to move the switch arm F between the horizontal and vertical positions. Metal segment B would rotate between contacts C opening/closing these contacts. These contacts can be seen on the drawing to the right.

   The schematic at the bottom gives a hint at the actual hookup to an antenna and receiver. Some of the contacts would protect the sensitive crystal detector, others would short out the headphones, others would swap the antenna back and forth, others would apply power to the transmitter's step up transformer and so on. Lots happening.

   The battery box supplied a bias voltage to the diode. This bias moved the signal higher up the slope of the diode's characteristics to get more of a current swing into the operators headphones.

Drawings from "Practical Wireless Telegraphy" by Elmer E. Bucher, 1917 edition

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