Improved Hoverman called GRAY-HOVERMAN
Well I have finally completed the modeling of the Hoverman UHF antenna.
I started with the original patent by D.R. Hoverman (# 3148371 granted on Sept8 1964).
The initial modeling results of the original patent with 4 pair of collinear reflectors, indicated the gain was less than the highly recommended commercial antenna by Channel Master CM-4221.
Since the CM-4221 uses a screen reflector of 20"x36", it seemed reasonable to expect better gain with the Hoverman, using a screen reflector. However, I liked the Hoverman with rod reflectors, since it is easier to build and has much less wind loading. So I experimented with adding more collinear reflectors to simulate a screen reflector and to my amazement found that by simply adding two more pair of collinear reflectors, a significant improvement resulted in the gain characteristics as well as a modest improvement in the F/B ratio.
I have dubbed this as the "Gray-Hoverman" antenna.
Using the EZNEC v3.0 modeling program, I was able to compare this 6 pair reflector array (Single and Double bays) with the CM-4221, using the cm4221a.ez modeling file by kq6qv, available at his hdtvprimer.com website.
Summary Results
===============
SingleBay Gray-Hoverman is better than CM-4221 over Ch 14-44 range !!
DoubleBay Gray-Hoverman up to +2.3 dB over SingleBay
The comparisons of gain are shown in the Gain vs Freq photo.
EZNEC v3.0 results are only given in tabular form, so I made a best-fit graph, which shows the EZNEC v3.0 results for:
1. Hoverman Array Only
2. SingleBay Gray-Hoverman with 6 pair collinear reflectors
3. DoubleBay Gray-Hoverman (vertical stacked) with 11 pair collinear reflectors
4. Channel Master CM-4221
Photos of the Polar plot at 500 and 660Mhz are shown as well as the swr plot, as calculated by EZNEC v3, for the Original Hoverman patent, SingleBay Gray-Hoverman and Channel Master CM-4221.
Interesting to note the polar plots of the Original patent vs SingleBay. The increase in gain is significant and you can see the improvement in the F/B ratio. The beamwidth of the SingleBay is 38.2 degrees vs 47.2 for the CM-4221.
I have also include a photo of the Gray-Hoverman dimensions. The Double Bay uses the same reflector and array dimensions. The spacing between the arrays is 127mm.
The model used elements made with #9 Aluminum solid wire (1/8" diameter).
I'd recommend using #9 Aluminum solid wire, as it is light but rigid and somewhat corrosion resistant.
You could also use wire coat hangers. Probably need 8 hangers for a SingleBay. Remember to scrape and clean the wire at the connection points.
Dimensions for the SingleBay Gray-Hoverman Antenna Copyright 2008, and distributed under the GPLv3 license
Dimensions for DoubleBay Gray-Hoverman Antenna Copyright 2008, and distributed under the GPLv3 license
On my prototype build, I used a 1" OD pvc pipe as the boom.
The rod reflectors and array are attached to insulators (70x25mm) made from plastic cutting board. (The plastic cutting board, purchased at a dollar store, was 24x14cm and 6mm thick. It was cut using a hand bench saw)
The array was attached to brackets, made from galvanized metal strapping, that went around the pvc pipe and was formed to mount the insulator at the reflector spacing distance of 100mm.
Please post your reception results, if you try this Gray-Hoverman antenna.
Regards
...Autofils