I looked over that design. But doesnt reducing the array angle go against Doyt Hoverman's and your own original findings ? So tuning the co-linear rods really changed all that ?
Don't fall into the trap of assuming Hoverman's original statements about the array angle stated in his patent, as being totally true for all cases.
When I first modeled generation 1 SBGH for UHF, I did look at the effect of reducing the angle and indeed found that for the UHF design, the gain was reduced with half-angles less than 45 degrees. That validated Hoverman's patent claim and hence there was no apparent value in reducing the array half-angle for the UHF design.
Since fading from this forum, I have been exploring two private projects:
1. GH version for WiFi (~2400 Mhz)
2. GH version for FM (88-108 Mhz).
A normal GH4 FM antenna (half-angle of 45), had a total height of over 200 inches. The gain/swr was excellent with net gain around 12dBi, but.... it is obviously just not practical.
That's when I began investigations on the GH with reduced half-angles.
While this produced a "useable" FM antenna, the total height is still over 80 inches, which is too much to fit in my attic.
That lead to a Combo FM/VHF-Hi GH4 design with a total height of about 53 inches. As you can appreciate, most combos force trade-offs, where the gain is reduced due to maintaining a low swr for the 2 to 1 frequency coverage ratio. The FM gain of this combo is nothing near 12dBi, but it is higher than the single quad FM presently being used, which receives 89.5 (NCPR Potsdam, NY) well in mono, but noisy in stereo mode. I'm about ready to try this combo in my attic; I'm expecting much better FM stereo reception.
As a result of this work, the next step was a reduced half-angle GH4 designed just for the 174 to 216 Mhz bandwidth. That design was posted recently as the GH4 Small Footprint VHF-Hi design.
The model results of gain/swr looks quite good, considering the overall size of 41"h x 86"w, but I have not tested any proto builds.
This VHF-Hi design could use some further optimizations, and I suspect an optimized GH6 version might show better results than any of Ken Nist's models of commercial antennas for Ch 7-13.
Out of interest, I also posted a GH4 UHF design with an reduced array angle of 35 degrees, and was surprised to see quite a reasonable gain for a total height of 24.2 inches. This might have applications, for those who need both VHF-Hi and UHF on a single mast, and want to keep total overall height under 6 ft.
Finally, let me close out my discussion of array half-angles:
For very high frequencies, such as WiFi, it might be an advantage to stretch the array rather than squish it, and that is what I am currently investigating for my WiFi GH antenna.