UHF (+ Hi-VHF) 2-Bay Hentenna with NO Reflector and with 11 Reflector Rods analyzed using 4nec2.
a) UHF 2-Bay Hentenna with NO Reflector: Analyzed Xauto's version x1052 2-Bay Hentenna: 8.75-in Width x 13-in Height. Raw Gain = 3.8-5.7 dBi, SWR under 1.8.
b) UHF 2-Bay Hentenna with with 11 Reflector Rods: dcartier's original 4nec2 file (UHF Gain & SWR Optimized: Score=1.16102) was run for another 30 hours of optimization (Score=0.660617), using nikiml's Python Scrips, significantly improving F/B & F/R Ratios.
UHF Raw Gain increased about 0.5 dBi. SWR slightly improved from under 2.2 to under 1.8. F/B and F/R were significantly improved, from a range of 3-7 dB to a range of 7-13 dB.
Hi-VHF Raw Gain was 7.1-5.5 dBi FORWARD and 7.1-8.2 dBi towards the REVERSE. Unfortunately SWR was very excessive (25-35).
FYI: Temporarily removing GW40 (wire only 0.5-in behind the feedpoint) increases SWR to 4.3. I've seen this sort of closely coupled "SWR tuning element" technique used in Yagi Antennas, including the YA-1713:
BTW: I temporarily commented out GW49 & GW50 (small, upper & lower most Reflector Rods) and reran 4nec2. I was surprised to see that SWR was unchanged, but Gain increased about 0.5 dBi and F/B & F/R Ratios were slightly improved....so, there may be TOO many Reflector Rods....go figure....
More (or Fewer?) Reflector Rods may be required to improve the UHF F/R & F/B Ratios... It is left as an exercise to optimize both UHF and Hi-VHF...preferably, including both F/R & F/B Ratios explicitly in the "cost function"....longer runs might also help....
EDIT (5Sep2011): Added UHF 2-Bay Hentenna (Square Loop) with NO Reflector.
Date(s): 21 Aug 2011. Album by holl_ands. 1 - 30 of 30 Total. 10834 Visits.
enlarge 55KB, 743x1024 1 UHF 2-Bay Hentenna with NO Reflector 3D View
enlarge 205KB, 808x1024 2 UHF 2-Bay Hentenna with NO Reflector 8.75-inch Width x 13.0-inch Height [1 small box = 0.25-inch] [1 big box = 0.25-inch]
enlarge 283KB, 1024x696 3 Twin-Hoop Chireix vs "Figure-8" Twin-Loop vs Shorted-Bowtie-Loop (SBL) vs 2-Bay Hentenna vs 6-Whisker Bowtie vs Single Loop. In decreasing UHF Gain order.
enlarge 131KB, 1152x638 4 UHF 2-Bay Hentenna with NO Reflector UHF Raw Gain = 3.8 to 5.7 dBi
enlarge 151KB, 1152x638 5 UHF 2-Bay Hentenna with NO Reflector UHF SWR (300-ohnms) under 1.8
enlarge 163KB, 1152x638 6 UHF 2-Bay Hentenna with NO Reflector UHF Impedance
enlarge 319KB, 1024x1024 7 UHF 2-Bay Hentenna with NO Reflector Azimuthal Pattern at 470 MHz
enlarge 321KB, 1024x1024 8 UHF 2-Bay Hentenna with NO Reflector Azimuthal Pattern at 590 MHz
enlarge 321KB, 1024x1024 9 UHF 2-Bay Hentenna with NO Reflector Azimuthal Pattern at 698 MHz
enlarge 70KB, 652x1024 10 Two-Bay Hentenna with 11 Reflector Rods holl_ands mods to dcartier 4nec2 file 3D View
enlarge 213KB, 726x1024 11 Two-Bay Hentenna with 11 Reflector Rods Front View [1 small box = 1-inch] [1 big box = 5-inches]
enlarge 58KB, 208x1024 12 Two-Bay Hentenna with 11 Reflector Rods Side View [1 small box = 1-inch] [1 big box = 5-inches]
enlarge 151KB, 1152x609 13 Two-Bay Hentenna with 11 Reflector Rods UHF Raw Gain
enlarge 176KB, 1152x609 14 Two-Bay Hentenna with 11 Reflector Rods UHF SWR (300-ohm) under 1.8