Antennas and Transmission Lines

Antennas and transmission lines used in long-distance point-to-point radio communication are described. Long wavelengths (3000 to 23,000 meters) were used exclusively in the early days of transoceanic communication, and are still used for specific services. The design parameters of long-wave transmitting antennas are briefly mentioned. This is followed by a description of some of the directive antennas used for reception of long waves to reduce the effects of atmospherics and interference. The discovery in 1924 that portions of the short-wave spectrum (10 to 100 meters) could be used for long-distance transmission during daylight as well as at night, completely revolutionized longdistance radio communication. The development of arrays and long wire types of antennas for short-wave transmission and reception are described. The radiation of undesired sidelobes from long wire types of antennas is discussed and means which have been used to reduce these side lobes are described. The parameters which enter into the design of open-wire and coaxial transmission lines are briefly presented. Finally, trends which may tend to reduce the extreme congestion of the short-wave spectrum are mentioned.