Ch14-17 18-Element Folded Dipole Yagi with Corner Reflector (20 Reflector Rods) analyzed using 4nec2. Dimensions (see 4nec2 File) determined using nikiml's Python Optimization Scripts. Two alternaive Geometries were investigated: the Conventional Corner Angle Reflector and a Free Form Search for the "Best" arrangement of RANDOMLY placed Reflector Rods, subject to just a few placement Constraints. Boom Length = 112-in was intentionally constrained by an non-linear exponential term in the Python Optimization Script's Target Function.
On Ch14 Raw Gain = 18.6 dBi, F/B & F/R Ratio = 29.9 dB and SWR (300-ohms) under 1.1.
###################################### a) FREE FORM PLACEMENT OF REFLECTOR ROD PAIRS: Dimensions determined using nikiml's Python Optimization Scripts, using RANDOM placements of Reflector Rod (RR) PAIRS (symmetric about the Boom) where Optimizer randomly selects Y-Coordinate Length (12 to 50-in) and X-Z Coordinates within fol. CONSTRAINTS: i) 18-El Yagi no Longer than about 110-in, ii) 4 RR Pair between X = -10 and 20-in and Z = +/- 36-in, iii) 3 RR Pair between X = -10 and 40-in and Z = +/- 40-in, iv) 3 RR Pair between X = -10 and 150-in and Z = +/- 40-in.
Final DOUBLE-ANGLE configuration is shown below, with five RR pairs in nearly Vertical Row behind the Yagi's Reflector, one RR Pair in close proximity above/below the Active Folded Dipole, with the remaining one SHORT RR pair and 3 LONG RR pairs further forward, on a rough approximation to a Double-Angle Reflector, although proximity to Max-Z may be limiting their ultimate configuration.
UHF Raw Gain = 18.0 dBi on Ch14-17 is LESS than Corner Reflector above. [Adjusting Optimization Parameters can probably improve on this Preliminary FIRST RUN.]
###################################### b) PARABOLA PLUS ADDITIONAL RR REFLECTOR: Prior to forming final configuration above, there was a preliminary configuration with five RR pairs forming a Parabolic shape in close vicinity of Yagi's Rear Reflector, which is also shown below. UHF Raw Gain was only somewhat lower: 17.9 dBi.
CORRECTION (22 Nov 2013): Images were ALL replaced by 20 RR (vice incorrect 14 RR) version.
ADDENDUM (22 Nov 2013): First, preliminary run for RANDOM placement of Reflector Rods was uploaded. Additional runs need to be conducted to see if Gain can come closer to Corner version.
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