UHF Horizontal 4-Bay (H4), aka 2x2-Bay Bowtie with 10 Reflector Rods analyzed using 4nec2 after determining "Best" Dimensions using nikiml's Python Optimization Scripts.
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).
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 model.
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 = 12.2 to 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....]
Horizontal Harness interconnecting the pair of 2-Bay Bowties was specifically designed for EQUAL Length in each wire by setting end points precisely in the Center of each Bay and then connecting from there diagonally to Feedline wires. Overall Harness Wire Length is changed in Optimization Scripts by moving Harness closer or further away from 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-in constraint (not shown).
Date(s): 21 Mar 2013. Album by holl_ands. 1 - 18 of 18 Total. 6705 Visits.
enlarge 40KB, 791x1024 12 UHF 2x2-Bay Bowtie - 10 Refl Rods 4nec2 File Contents of Python Optimization Control *.bat (text) file at end of File.
enlarge 188KB, 1152x692 13 UHF 2x2-Bay Bowtie - 10 Refl Rods Hi-VHF Raw Gain Typ 6.5-7.3 dBi Hi-VHF F/B & F/R Ratio Typ=10, Min= 7 dB Note Narrow Gain Hole on Ch9
