Rotary Spark Gap

1910 Replica 1/2 KW Synchronous rotary gap transmitter. This image was 'Photo of the year' in QST magazine, and used in the 2011 ARRL annual calendar. I retain copyright. Blow the image up and view the rear electrode. It is firing at 1800 arcs per minute. Current in the arc is approximately 1,000 amps.

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