Hi-VHF+UHF 2-Square Centipede Inside Boxed-Twin-Rectangular-Loop (NO Reflector) analyzed using 4nec2.
UHF Raw Gain = 7.5 to 10.6 to 7.6 dBi and SWR (300-ohms) under 2.1. [Excellent] Hi-VHF Raw Gain = 4.8 to 5.2 dBi and SWR (300-ohms) under 1.9. [Excellent]
Based on 4nec2 file posted by MagiMaster on 8Nov2013, plus my mods to add FR+RP Plotting Statements and add Rsrc to Tweak AGT (was off by only 0.1 dB): http://www.digitalhome.ca/forum/showthread.php?p=1881665
Plus Horizontal Elements connected to SOURCE Wire that turn it into Bokabob's Centipede-1: http://www.digitalhome.ca/forum/showthread.php?p=1053924
For this improved version, I also "Boxed In" the Rectangular Loop, shrinking the interior whilst also adding an additional "Top Hat". When running nikiml's Python Optimization Scripts, I allowed the Inner Antenna to slide up and down within the Rectangle until it was clear that the "best" solution was perfectly centered (e.g. Zs=0.0), so the upper & lower parts are Twins.
Numerous "trials" were observed to have been discarded because the Python Scripts detected an Overlap between the Outer & Angular Bars if they were within about 1/4+ inches. But since Z-Coordinates would need to be matched to AT LEAST two and probably more decimals, random picks didn't stumble into a condition where the Scripts would detect the Intersect...so I forced it as depicted below. A significant Loss of Gain on 470 MHz was the only disadvantage of the forced Intersect.
Running a 4nec2 Parameter Sweep on the Gain Peak frequency revealed that the best Gain occurred when Outer and Angular Bars were very close....but NOT connected.
Date(s): 12 Nov 2013. Album by holl_ands. 1 - 27 of 27 Total. 1811 Visits.
enlarge 97KB, 675x1024 1 2Sq-Centipede-In-BoxedTwinRectLoop 3D View
enlarge 243KB, 688x1024 2 2Sq-Centipede-In-BoxedTwinRectLoop Front View [1 large square = 2.5 inches]
