The authors present experimental verification of an improved directivity element (the Corum element) for controlling the elevation plane directivity of a vertical monopole element. The results suggest that, if an image plane version of the Corum element is used to surround an existing tower, the resulting antenna will improve the sky-wave suppression in all cases, with a modest increase in ground wave. While performing an antifade engineering study for a broadcast antenna at 530 kHz, the authors decided to run a study on a typical 1 kW GWEN (ground-wave emergency network) station (300 ft tower in the 160-190 kHz band). It was found that the Corum element makes a significant improvement in useful GWEN coverage. >

Experimental validation of the 'improved directivity element'-elevation plane control

UWB antenna and MIMO antennas with bandwidth, band‐notched, and isolation properties for high‐speed data rate wireless communication: A review

An asymmetric vertical dipole is proposed as an MF AM-broadcast station transmitting antenna. This kind of vertical dipole antenna uses the supporting guys as part of the radiating structure permitting an efficient radiation with a strong surface wave. It produces less high-angle radiation compared to a classic buried-ground-plane monopole of similar height. Analysis data for near fields and power density of monopoles, elevated ground plane monopoles, and asymmetric vertical dipoles are presented graphically to explain why this last antenna can match the radiation efficiency of the classical monopole without a buried ground plane. Good agreement between calculation and measurements is achieved in all cases studied. >

MF AM transmitting asymmetric vertical dipole

A new type of broadcast antenna is described which radiates very little energy over a wide, high angle. The angle above which minimum energy is radiated can be varied electrically from 40° to 60°, thus permitting the fading wall to be adjusted for maximum primary service. The electrical height of the antenna is dependent upon the specific vertical pattern desired but is approximately 300°. The results of experiments with small model antennas are in good agreement with theory.

An Antenna for Controlling the Nonfading Range of Broadcasting Stations

The nocturnal service area, or distortionless area, of MF AM broadcast stations depends on the radiation properties of the transmitting antenna and the physical constants of the ground surrounding the transmitting site. These ground constants limit the maximum antenna height and establish how large the nocturnal service area will be. In some instances the nocturnal service area can be increased by the use of vertical antenna array. In this case it is very important to know the increase of the theoretical nocturnal service area of the station and if the use of more sophisticated radiating systems is justified. Calculations were made to determine the theoretical nocturnal service area of a station using vertical arrays, and curves with maximum distortionless distance are given as a function of frequency and ground physical constants. Measurements on reduced-scale models in HF and VHF bands are described, and improvements in antenna antifading properties and in nocturnal service area are shown. >

The nocturnal service area of MF AM broadcast stations using vertical arrays

During the past several years, the trend in broadcast transmitting antennas has been towards the vertical radiator. The performance of these newer antennas has been subject to considerable theoretical discussion. This paper, however, emphasizes the actual field results obtained with tower radiators, and presents data on efficiency, base voltage, base loss, practical design considerations, and cost. It is concluded that the conventional broadcast antenna supported by two towers, as used in the past, is definitely outmoded by the single vertical radiator, or, in special cases, by a combination of vertical radiators in a directional array. Antennas used in the broadcast band only, 550 to 1500 kilocycles, are considered.

http://ieeexplore.ieee.org/iel5/5547934/35520/01685990.pdf

W.B. Lodge

Papers

The Broadcast Antenna