Multiplex Radio Telegraphy and Telephony

The authors classify the chief methods of multiplex radio communication as multi-radio frequency, mono-radio-frequency with multi-audio-frequency, and mono-radio frequency modulated at several super-audio-frequencies each of which is itself modulated at audio frequency. The authors classify antenna systems for the first method as of the series loop type, the branch type, and the mesh type. Each of these systems has zero reactance at a number of radio frequencies. The series type is investigated mathematically for several cases and checked experimentally with good accuracy. Duplex and quintuplex radio telephony and telegraphy over 5 miles (8 km.) at wave lengths around 2,000 meters were experimentally accomplished, and are described.