Broadband base isolated asymmetrically fed VHF antenna
Abstract
Antennas presently being used for vehicular military VHF communications are narrowband. New generation frequency hopping radios, however, require broadband antennas. The antenna must be base isolated in order to reduce undesirable pattern nulls and impedance variations caused by currents induced on the support structure. Physical constraints limit the antenna length to ten feet while operating from 30 MHz to 88 MHz. To satisfy the above requirements a model of a broadband base isolated, cylindrical antenna less than three meters long was analyzed and built. Equations for the current distribution as a function of the physical parameters were formulated and solved. The antenna selected as most optimum, i.e., maximum gain on the horizon, was 2.5 meters in length and fed 1.0 meters above the mounting surface. The most optimum base isolation network consisted of a coaxial cable choke wound on a ferrite toroid. The cable choke was made resonant at 25 MHz with minimum distributed capacity.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1983
- Bibcode:
- 1983PhDT........30C
- Keywords:
-
- Antennas;
- Broadband;
- Frequency Hopping;
- Military Operations;
- Radio Communication;
- Very High Frequencies;
- Antenna Feeds;
- Coaxial Cables;
- Current Distribution;
- Communications and Radar