20-40-Kilowatt High-Frequency Transmitter

The rapid growth in the use of high frequencies for long-distance communication has been nothing short of phenomenal. One of the major parts of the high-frequency communication system is the transmitter converting 60-cycle power into a frequency in the order of millions of cycles. Although the first communication work on short waves was accomplished by the radiation of a few watts, reliable and rapid communication requires power of the order of tens of kilowatts. The technique in producing a transmitter of relatively large power to feed an antenna for radiating high frequencies has been found to be quite different from that required for previous design and test of radio transmitters. This paper presents the results of intensive work of the last two years. It describes some of the interesting problems which have had to be solved. Not least among these problems were the methods of providing a satisfactory artificial load for factory test, the determination of keying characteristics, and the design of the frequency control units.