Extended Hoverman HDTV UHF antenna
The design presented here is an alternative to a double-bay Hoverman antenna. It has a very high gain but a much narrower bandwidth at its design frequency. Pictured below is a schematic of the proposed antenna (dubbed X-GH8) along side the single-bay GH-10 for comparison.
The version of the X-GH8 presented here has been optimized for 615 MHz. The following plots show its predicted net gain (corrected for the SWR effects), front-to-back ratio, and the SWR across the post-February 2009 UHF band. For comparison, the plots also include curves for the GH-10. As the plots show, this antenna has a narrow bandwidth and is effective only for frequencies near its design frequency where it has a net gain in excess of 18 dBi. The gray region corresponds to the frequency range where the net-gain is above 14 dBi.
The high gain is achieved by flattening the radiation pattern toward the horizon. As such, the care should be exercised when vertically aligning the antenna.
The geometric parameters of the X-GH8 was found by optimization process outlined on the Antenna Overview page. The antenna consists of two parts: a driven element formed by a zigzag pair, and a reflector made up of a varying number of horizontal parasitic elements.
The figures and tables provided below give the detailed geometric information about the antennas. Each of the tables contains a `D' parameter, which represents the diameter of the wire to be used. In addition, the tables for the zigzag driven element contains a ` Δx' entry that represents the spacing between the driven element and the reflector.
The feedpoint, denoted by the orange segment connecting the zigzag pairs, has a 300 ohm impedance. As such, a 300 ohm matching transformer will be required to connect this to standard 75 ohm cable (RG-6).
This page was last updated Jan 5, 2014 by John E. Davis. To comment on it or the material presented here, send email to jed at jedsoft org.