VHF-UHF Fixed Station Mast Mounted Antennas System
Abstract
The purpose of this program is to design, build, test and deliver a VHF-UHF fixed station mast mounted antenna system. Antenna Products proposed three configurations to investigate in an effort to achieve an acceptable system. Configuration A consisted of combining a VHF monopole/counterpoise antenna and a UHF collinear antenna. During the investigation it was found that the counterpoise did not properly terminate the radiating structure when the radials are less than a quarter wavelength long. The performance is characterized by a loss of gain at the lower frequencies. A full size structure would be larger and heavier than a dipole antenna. Therefore, no further investigation of configuration was undertaken. Configuration B consists of combining a VHF vertical half-rhombic antenna system and a UHF collinear antenna. The rhombic antenna system was envisioned as two rhombic curtains mounted orthogonally about a 10 meter mast and would serve as guys for the mast. The UHF antenna would mount on top of the mast. It has been determined that to achieve reasonably omnidirectional azimuth patterns it is necessary to use four rhombic curtains in an azimuth array. At the interim report, the height of the antenna was 10 meters and the radius was 25 meters. Further investigations have lead to a 10 meter tall structure with 10 meter radius that uses six equally spaced slant wires that are fed in-phase near ground and connected at the top of the tower. A UHF collinear dipole array mounts on top of the dielectric mast. A prototype of this antenna is available for shipment to CECOM for further evaluation. The propagation mode for this antenna is surfacewave instead of spacewave as commonly experienced when two antennas are mounted on masts above the earth's surface. Therefore, field tests should be conducted to determine the suitability of the antenna for the application.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 14, 1998
- Accession Number
- ADA355616
Entities
People
- Ross L. Bell