The Determination of Power in the Antenna at High Frequencies

Following a brief review of general methods of measuring radio-frequency power in the antenna, a series of tests on a particular transmitter operating from 4000 to 26,000 kc is described. These tests indicate that it is reasonable for such a transmitter continuously variable in frequency and of fairly modern design to be expected to put not less than 50 per cent of its input plate power of the last stage into the antenna as radio frequency from 4000 kc to 8000 kc and not less than 32 per cent at 24,000 kc. Intermediate efficiencies are indicated for the intervening frequencies. Coil losses and stray losses have been separated and the indications are that with modern insulation a moderate increase in efficiency can be expected in a transmitter designed for as high L/C ratio as possible, which is particularly feasible in the case of a transmitter operating on only one frequency. Marked increases in efficiency in the upper end of the spectrum can only be expected by the use of tubes better adapted to the upper frequencies.