Elevated vertical monopole antennas: effects of changes in radiator height and radial length

Computer analysis and field tests indicate that an elevated vertical monopole with elevated horizontal radials can provide ground-wave field intensities which are comparable to those generated by a conventional ground-mounted monopole with 120 buried radials. Computer modeling was used to investigate the effects of changes in monopole height and radial length on the transmitted field intensity. The tower height was varied in 45-degree increments from 45° to 225° as was the length of the four elevated horizontal radials. Born the direct and isolated feed methods were utilized, and elevation heights of 5 m and 10 m were modeled. The results show that 90° radials generally give the strongest field strength, irrespective of the radiator height or the feed method. Isolated feed was usually somewhat better than direct feed, and an elevation height of 10 m was slightly superior to a height of 5 m in most cases. Taller towers always produced higher maximum values of electric field strength. Conventional antenna systems with various heights and radial lengths were also modeled to serve as a baseline reference