Gray-Hoverman, the wideband TV antenna

 Author:   Posted on:   Updated on:  2017-10-30T11:15:58Z
Air TV channels broadcast on frequencies ranging from 170 MHz to 860 MHz. The VHF-Hi band covers 175 to 230 MHz, while UHF covers 470 to 860 MHz. The gap between is used for cable TV. Receiving all these frequencies is difficult when using a single antenna.

The Gray-Hoverman antenna has been designed by Doyt R. Hoverman and it was patented in the sixties. His design only covered a part of UHF band. However, with some improvements, the antenna can receive well both the UHF as well as VHF-Hi. This post will a simple to build variant of the antenna that can be used to receive 170 to 230 MHz channels (5 - 12) and a part of UHF between 470 - 720 MHz (21 - 52 channels) with a minimum gain of 5 - 6 dBi. There are however designs that offer a minimum gain of 8 dBi on VHF and 10 dBi on UHF (check the Links section). This antenna can be used for any kind of signal that can be received on the mentioned frequencies: analog TV, DVB-T, DVB-T2, ISDB-T, ATSC. The design is distributed according to the GNU GPL version 3 license.
Gray-Hoverman with NARODs, the wideband TV antenna
Gray Hoverman antenna with NARODs for VHF (drawing)
Gray Hoverman antenna with NARODs
The antenna can be built with aluminium or copper of 3 to 8 mm diameter. It should be noted that the NAROD elements are needed only if you want to receive VHF band. The gain of this antenna is shown below (4nec2 simulation).
Gain (dBi) of Gray-Hoverman antenna with NARODs (4nec2 plot)
Gain (dBi) of Gray-Hoverman antenna with NARODs
The antenna impedance is 300 ohms balanced. A balun should be used. You can buy one or you can build one similar to those in commercially available antenna amplifiers. If you don't have the parts for it, you can omit it and connect the cable directly, although it is highly recommended to use one.

Wideband VHF/UHF impedance adapter (balun)
The balun
Detailed instruction about how to build this matching transformer can be found at: Make a wideband antenna matching transformer.

The performance of the antenna can be improved by adding some reflectors. See the designs here. No reflector variant is easier to build and receives two sides. See its radiation pattern below.
Radiation pattern of no reflector Gray Hoverman antenna
Radiation pattern of no reflector antenna
A construction variant is shown below. The antenna sits vertically, as shown.
Gray Hoverman antenna with NARODs (construction detail)
Construction detail. 1. Duct tape 2. Pass through hole to prevent a cable position that would allow water to enter and oxidize the cable wires.
For an easy way to build those NARODs (the horizontal "hat"-like elements) see unclesam's bending jig on Instructables [5].

Have you built this antenna? How does it perform for its simplicity?

Links

  1. Wikipedia. Television channel frequencies.
  2. The Gray-Hoverman Antenna for UHF Television Reception - Digital Home Canada
  3. Nikolai Mladenov. nikiml's Antenna pages.
  4. SBGH-6 Tophat NARODs for VHF-Hi (on WayBack Machine - unfortunately, full size images were not indexed).
  5. unclesam. NAROD Bending Jig for Gray Hoverman TV Antenna (CC-BY-SA). Available on Instructables.
  6. Новые антенные усилители. RadioRadar.net

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