Hi-VHF Circular Loop with either Loop or Screen Reflector analyzed using 4nec2.
a) With Loop Reflector, Net Gain was 8 dBi on Ch7, dropping to 6 dBi on Ch13 with excellent SWR, except for small increase on Ch7.
Adding Loop Reflector increased Net Gain by 2-4 dB (less at high freqs) with more than 8.7 dB F/B (and F/R) using
Optimum Diameter=22-in for Half-Inch Copper Tubing. Best F/B (and F/R) is on Ch8-10.
Optimum Diameter=21.5-in for Quarter Inch Copper Tubing (QICT) was nearly as good, with more than 7.3 dB F/B (and F/R). Smaller Circular Loop Element sizes not analyzed since a Square Loop (Quagi) would be easier to construct.
Loop Reflector dimensions are optimized for full Hi-VHF Band coverage. Rescaling to optimize Ch7 will have only minor-moderate impact to Ch13 F/B, F/R and SWR. However, rescaling to optimize Ch11-13 will degrade F/B, F/R and especially SWR on CH7-10.
b) EDIT (16 Sep 2009): Added analysis of alternative Hi-VHF Circular Loop with Minimalist 28" H x 34" W Screen Reflector:
Hi-VHF Raw Gain = 7.9 dBi, F/B & F/R Ratio = 11.5 to 15.2 dB and SWR (300-ohms) Under 3.2.
c) EDIT (5 Oct 2013): Added analysis of alternative Hi-VHF Loop with 40" H x40" W Screen Reflector to improve F/B & F/R Ratios:
Hi-VHF Raw Gain = 8.2 to 8.3 dBi, F/B & F/R Ratio = 13.7 to 15.5 dB and SWR (300-ohms) Under 2.7.
d) EDIT (15 Jul 2014): Added Circular Polarization analysis of alternative Hi-VHF Loop with 28" H x 34" W Screen Reflector.
Date(s): 15 July 2009. Album by holl_ands. 1 - 43 of 43 Total. 9558 Visits.
enlarge 0KB, 1024x840 1 Hi-VHF Circular Loop w. Loop Reflector - 3D View Loop to Loop Separation = 13-in
enlarge 0KB, 1024x696 2 Hi-VHF Circular Loop w. Loop Reflector Raw vs Net Gain vs SWR (300-ohm) for Half-Inch and QuarterInchCopperTubing (QICT).
enlarge 0KB, 1024x696 3 Hi-VHF Circular Loop w. Loop Reflector Dimensions are for a "balanced" design with EQUAL F/B and F/R at highest and lowest freqs.
enlarge 0KB, 1024x819 4 Hi-VHF Circular Loop w. Loop Reflector Raw Gain, F/B and F/R Ratios
Optimum Diameter=22-in for Half Inch Copper Tubing (OD=0.514)