UHF H4 2x2-Bay Bowtie - NO and 10 Refl Rods:
I uploaded 4nec2 results for a UHF Horizontal 4-Bay (H4), aka 2x2-Bay Bowtie with either NO or 10 Reflector Rods. Optimized Dimensions were determined by running a series of nikiml's Python Optimization Scripts, adjusting the Target Levels and esp. Target Function "weights" as necessary to find the desired balance of Raw Gain, F/B & F/R Ratio and SWR (Mismatch Loss). Each trial run takes 3-5 days on my Intel i7 (8 threaded) Alienware Laptop, so it's been a slow slog. Similar Horizontal Harness design for 8-Bays is in the works...."soonish"....
In preliminary Optimization searches, it became apparent that the lowest SWR performance was being found when there was either two Reflector Rods centered behind each Harness Wire. Or a Reflector Rod directly behind each Harness wire...as was designed into the below models.
Horizontal Harness interconnecting the pair of 2-Bay Bowties was specifically designed for EQUAL length in each wire by setting the end points precisely in the Center of each Bay and then connecting from there diagonally to the Feedline wires. The overall Harness Wire Length is changed in the Optimization Scripts by moving the Harness closer or further away from the plane of the Bowties and the Impedance is adjusted by the separation between the two Harness Wires.
The Optimization Script does a random search of ALL applicable variables to find the "Best" set of Dimensions which will maximize Raw Gain, F/R and F/B Ratios with an "acceptable" SWR level. In preliminary runs, slightly higher Raw Gain was found as separation between Left and Right 2-Bays was increased....however, forward sidelobe levels also increase to what I believe are unacceptably higher levels. Hence final Optimization search was limited to Center-Center 2-Bay Separation between 20-24 inches, with "best" result at my imposed maximum: 24-inches. Even better forward sidelobe suppression is found when Optimizing with 20-inch constraint (not shown).
a) UHF H4 2x2-Bay Bowtie - NO Refl Rods:
UHF Raw Gain Max = 12.8 dBi
UHF SWR (300-ohms) Max = 2.3
Note small amount of F/B Ratio on lower Channels due to Harness acting as a REFLECTOR.
b) UHF H4 2x2-Bay Bowtie - 10 Refl Rods:
Locating the Horizontal Harness BETWEEN the Bowties and the Reflector Rods provided 1.4 dB
MORE Raw Gain acting as a DIRECTOR than when placed in FRONT of the Bowties (since inferior,
will not be shown).
UHF Raw Gain Max = 14.8 dBi
UHF F/B & F/R Ratio Min = 20 dB
UHF SWR (300-ohms) Max = 2.4
UHF Beamwidth = 30 to 20-degrees, about half as much as an M4 4-Bay.
Hi-VHF Raw Gain Typ. 6.5-7.3 dBi
Hi-VHF F/B & F/R Ratio Typ. 7-10 dB
Hi-VHF SWR (300-ohms) is Excessive [Which may or may not be a problem in any given situation....]Edited by holl_ands - 3/21/13 at 1:25pm