This 1921 photo shows U.S. Forest Service radio operator F.K. Teeter, Jr., at his post monitoring for forest fires. The Forest Service had aircraft equipped with a 1.8 kw spark transmitter, with a trailing wire with a lead weight at the end. The entire transmitter was encased in a torpedo-shaped shell mounted on the running gear. Only the key and ammeter were inside the plane. The aircraft was not equipped with a receiver, and the ground stations were not equipped with a transmitter. Instead, the aircraft transmitted in the blind, using a code indicating the type of fire and location by township, section, and range.
The system was reported to give very satisfactory results.
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