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 holl_ands | Home > Loop Antennas incl Folded Dipole > 
Hi-VHF Circular Loop + Reflector
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. 9763 Visits.
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Hi-VHF Circular Loop w. Loop Reflector - 3D View
Loop to Loop Separation = 13-in


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Hi-VHF Circular Loop w. Loop Reflector
Raw vs Net Gain vs SWR (300-ohm) for Half-Inch
and QuarterInchCopperTubing (QICT).


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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.


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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)


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Hi-VHF Circular Loop w. Loop Reflector - SWR

Optimum Diameter=22-in for
Half Inch Copper Tubing (OD=0.514)


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Hi-VHF Circular Loop w. Loop Reflector
Impedance

Half Inch Copper Tubing (OD=0.514)


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Hi-VHF Circular Loop w. Loop Reflector
Raw Gain, F/B and F/R Ratios

Optimum Diameter=21.5-in for
Quarter Inch Copper Tubing


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Hi-VHF Circular Loop w. Loop Reflector - SWR

Quarter Inch Copper Tubing


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Hi-VHF Circular Loop w. Loop Reflector
Impedance

Quarter Inch Copper Tubing


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DOC10
Hi-VHF Circular Loop w. Loop Reflector
Example 4nec2 File


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Hi-VHF Circular Loop 28x34 Screen Reflector
3D View


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Hi-VHF Circular Loop 28x34 Screen Reflector
Front View [One small box = 0.5 inch]
23-in Diameter (Ctr-Ctr) QICT
(Quarter Inch Copper Tubing)
28"H x 34" W Screen Refl. (1-in x 2-in Grid)


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Hi-VHF Circular Loop 28x34 Screen Reflector
Side View [One small box = 0.5 inch]
Loop to Reflector Separation = 13-in

"Small note: Reflector's top looks 1..."
View Comments...

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Hi-VHF Circular Loop 28x34 Screen Reflector
Top View [One small box = 0.5 inch]
Loop to Reflector Separation = 13-in


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DOC15
Hi-VHF Circular Loop 28x34 Screen Reflector
Example 4nec2 File


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Hi-VHF Circular Loop 28x34 Screen Reflector
Hi-VHF Raw Gain = 7.9 dBi
Hi-VHF F/B & F/R Ratio = 11.5 to 15.2 dB


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Hi-VHF Circular Loop 28x34 Screen Reflector
Hi-VHF SWR (300-ohms) Under 3.2


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Hi-VHF Circular Loop 28x34 Screen Reflector
Hi-VHF Impedance


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 174 MHz


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 198 MHz


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 216 MHz


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Hi-VHF Circular Loop w. Screen Reflector
Right Hand Circular Polar. at 174 MHz


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Hi-VHF Circular Loop w. Screen Reflector
Right Hand Circular Polar. at 198 MHz


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Hi-VHF Circular Loop w. Screen Reflector
Right Hand Circular Polar. at 216 MHz


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Hi-VHF Circular Loop 28x34 Screen Reflector
Ch2-6 + FM Band Raw Gain


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Hi-VHF Circular Loop 28x34 Screen Reflector
Ch2-6 + FM Band SWR (75-ohms) is EXCESSIVE


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Hi-VHF Circular Loop 28x34 Screen Reflector
Ch2-6 + FM Band Impedance


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 54 MHz (Ch2)


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 69 MHz (Ch4)


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 87 MHz (Ch6 & Lo-FM Band)


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 97 MHz (Mid-FM Band)


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Hi-VHF Circular Loop 28x34 Screen Reflector
Azimuthal Patterns at 108 MHz (Hi-FM Band)


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Hi-VHF Circular Loop w. Screen Reflector
Right Hand Circular Polar. at 186 MHz


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Hi-VHF Circular Loop 40x40 Screen Reflector
3D View
23-in Diameter (Ctr-Ctr) QICT
(Quarter Inch Copper Tubing)


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Hi-VHF Circular Loop 40x40 Screen Reflector
Front View [One small box = 1.0 inch]
23-in Diameter (Ctr-Ctr) QICT
(Quarter Inch Copper Tubing)
40"H x 40" W Screen Refl. (1-in x 2-in Grid)


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Hi-VHF Circular Loop 40x40 Screen Reflector
Top View [One small box = 1.0 inch]
23-in Diameter (Ctr-Ctr) QICT
Loop to Reflector Separation = 14-in


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Hi-VHF Circular Loop 40x40 Screen Reflector
Hi-VHF Raw Gain = 8.2 to 8.3 dBi
Hi-VHF F/B & F/R Ratio = 13.7 to 15.5 dB


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Hi-VHF Circular Loop 40x40 Screen Reflector
Hi-VHF SWR (300-ohms) Under 2.7


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Hi-VHF Circular Loop 40x40 Screen Reflector
Hi-VHF Impedance


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Hi-VHF Circular Loop 40x40 Screen Reflector
Azimuth Pattern at 174 MHz


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Hi-VHF Circular Loop 40x40 Screen Reflector
Azimuth Pattern at 198 MHz


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Hi-VHF Circular Loop 40x40 Screen Reflector
Azimuth Pattern at 216 MHz


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Hi-VHF Circular Loop 40x40 Screen Reflector
4nec2 File


 
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holl_ands,

Did you notice the gain flatness of the screen reflector? I also noticed that it has a beamwidth of 70° down to about 5dB.

How do the results compare to a 21.5" (ctr-ctr) QICT driven element?
 - 
Systems2000, Thu, 15 Oct 2009 11:38AM