AN IMPROVED ANTIFADING MEDIUM-WAVE ANTENNA

In domestic medium-wave radio broadcasting it is necessary in many cas es to expand the circular service zones (undirected broadcasting). Thi s problem can be solved by using high-gain antifading antennas. Such a ntennas can be used to increase the radiated power by a factor of epsi lon (where epsilon is the antenna gain), to extend the zone of high qu ality, nonfading surface-wave reception at night, and to use more effi ciently radio frequencies assigned for radio-broadcasting purposes. It is also possible to use large antennas consisting of multiple section s fed in phase at several points. A three-section antenna 320 m high w ith a controlled current distribution and two feed points was develope d in 1971 [1, 2] and was subsequently constructed at one radio center. A more effective,antenna 420 m high consisting of 4 sections that was likewise fed at two points [3] was subsequently developed. The sectio ns of this antenna are mounted on a grounded mast to improve its mecha nical strength, particularly in regions with increased seismic activit y and to provide lightning protection. There are two versions of the f our-section antenna. The first version uses custom tuning in the optim al radiation pattern (RP) mode at any operating wavelength in the medi um-wave band. In the second version, the antenna is tuned in advance b y installing jumpers between the wire cylinders of the antenna and its mast at specific points. This version employs a simpler antenna struc ture and is recommended in cases where the antenna operates at a singl e wavelength for an extended period. This paper presents the results o f theoretical and experimental studies of the second version of the fo ur-section antenna employing a controlled current distribution fed at two points (the abbreviation ARRTZ-2/4, where 2 is the number of feed points and 4 is the number of antenna sections.