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 holl_ands | Home > Loop Antennas incl Folded Dipole > 
VHF Square & Circular Loops
VHF Square and Circular Loops are analyzed using 4nec2 to find optimum sizes.

Optimum size for Hi-VHF Square Loop is 20-inches per side (Center-to-Center)
for 1/2-in (Type M) Copper pipe (OD=0.569-in),
18.5-inches for 1/4-in Copper Tubing and 16.75-inches for AWG24 wire, which
would be less visible in a window.

Hi-VHF Square and Circular Loops are analyzed using 4nec2 to find optimum sizes.

Optimum size for Hi-VHF Circular Loop is 24-inches Diameter (Center-Center) using
"3/8-in" Copper Tubing (actual OD=0.514-in).  Despite smaller diameter,
Circular Loop had slightly higher Raw and Net Gain than Square Loop.

Optimum size for Hi-VHF Circular Loop using QICT (QuarterInchCopperTubing) is 23-in,
AWG12 is 21.5-in and AWG26 is 21-inches (very thin to invisibly tape to a window).

A 10-ft length of 1/2-in Copper Pipe and four 90-deg Elbows costs about $10.
"3/8-in I.D." Copper Coil for Circular Loop is even less.

=================================
Lo-VHF Circular and Square Loop Optimum Dimensions:
[AWG12 typ. for Indoors and HICT = Half-Inch Copper Tubing...or LARGER for Outdoors.]

Circular Loop Diameters:
Ch6 = 48.0-in [AWG12], Raw Gain = 3.6 to 3.8 dBi, SWR Under 2.5.
Ch3 = 64.5-in [AWG12], Raw Gain = 3.5 to 3.9 dBi, SWR Under 2.4
Ch3+4 = 64.5-in [HICT], Ch3 Raw Gain = 3.5 to 3.9 dBi, SWR Under 2.4.

Square Loop Lengths per Side:
Ch6 = 38.0-in [AWG12], Raw Gain = 3.3 to 3.5 dBi, SWR Under 2.5.
Ch3 = 51.0-in [AWG12], Raw Gain = 3.2 to 3.5 dBi, SWR Under 2.7.
Ch2 = 56.5-in [AWG12], Raw Gain is about 3.3 dBi, SWR Under 2.7.
Ch3+4 = 52.0-in [HICT], Ch3 Raw Gain = 3.3 to 3.6 dBi, SWR Under 2.7.

=================================
EDIT (16Jul2009): Analyzed additional element sizes for Hi-VHF Circular Loop.

EDIT (11Jun2013): Added Ch2 Square Loop analysis with Optimum Dimensions.

EDIT (4Jan2015): Added Circular Polarization Response Charts for 23-in QICT Circular Loop.

EDIT (28Mar2017): Added Optimized Circular and Square Loop Charts for
AWG12 (Indoors) and HICT (Outdoor).
Date(s): 16 July 2009. Album by holl_ands. 1 - 60 of 60 Total. 13786 Visits.
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Hi-VHF Square Loop - Colorized Gain

Red and Green colors in loop are modeling segments.


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Hi-VHF Circular Loop - without mount
23.75-in Diameter (Ctr-Ctr)
Using "3/8-in" Type L Copper Tubing (OD=0.514-in)
Metal-Metal Gap at bottom should be 3/4-in.


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Hi-VHF Circular Loop - without mount
Flattened and Drilled the Ends
Brass screws and nuts prevent corrosion.

Plastic/PVC mount will attach to screw holes
and (if outdoor) another connection at top.


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HiVHF Circular Loops - Raw/Net Gain & SWR
Optimum Diameter depends on Element Size.


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Hi-VHF Circular vs Square Loop
Raw/Net Gain & SWR

"3/8-in I.D." Circular has slightly higher Raw/Net Gain
despite being smaller diameter than 1/2-in Pipe.


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Hi-VHF Square Loop - AvgGainTest = 1.0
(Typical for all runs)
Verifies 4nec2 generates accurate results.


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Hi-VHF Square Loop - Raw/Net Gain & SWR
Optimum size is 20-in for 1/2-in Type M Copper Tubing.


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Hi-VHF Square Loop vs Folded Dipole
Compare Net Gain vs Element Diameter

Click to see hi-rez image.
Click "X" as usual to exit window.


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Hi-VHF Square Loop vs Folded Dipole
Compare SWR vs Element Diameter


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Hi-VHF Circular Loop - 23-in QICT
Hi-VHF Raw Gain = 3.6 to 4.4 dBi

Optimum size is 23-in for 1/4-in Type M Copper


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Hi-VHF Circular Loop - 23-in QICT
Hi-VHF SWR (300-ohms) Under 2.6


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Hi-VHF Circular Loop - 23-in QICT
Hi-VHF Impedance


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 174 MHz


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 198 MHz


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 216 MHz


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Hi-VHF Circular Loop - 23-in QICT
Circular Polarization Pattern at 174 MHz

TV/DTV Signals Follow RHCP Curve
(Right Hand Circular Polarization)


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Hi-VHF Circular Loop - 23-in QICT
Circular Polarization Pattern at 198 MHz

TV/DTV Signals Follow RHCP Curve
(Right Hand Circular Polarization)


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Hi-VHF Circular Loop - 23-in QICT
Circular Polarization Pattern at 216 MHz

TV/DTV Signals Follow RHCP Curve
(Right Hand Circular Polarization)


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Hi-VHF Circular Loop - 23-in QICT
Ch2-13 Raw Gain in FORWARD Direction

Below ~70 MHz, Gain is more toward SIDES


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Hi-VHF Circular Loop - 23-in QICT
Ch2-13 SWR (300-ohms) is Excessive
on the Lower Channels


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Hi-VHF Circular Loop - 23-in QICT
Ch2-13 Impedance


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 54 MHz


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 84 MHz


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Hi-VHF Circular Loop - 23-in QICT
Azimuthal Pattern at 96 MHz


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Hi-VHF Square Loop - Raw Gain
Optimum size is 20-in for 1/2-in Type M Copper


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Hi-VHF Square Loop - SWR
Optimum size is 20-in for 1/2-in Type M Copper


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Hi-VHF Square Loop - Impedance
Optimum size is 20-in for 1/2-in Type M Copper


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Hi-VHF Square Loop - Raw Gain
Optimum size is 18.5-in for 1/4-in Copper Tubing


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Hi-VHF Square Loop - SWR
Optimum size is 18.5-in for 1/4-in Copper Tubing


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Hi-VHF Square Loop - Impedance
Optimum size is 18.5-in for 1/4-in Copper Tubing


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Hi-VHF Square Loop - Raw Gain
Optimum size is 16.75-in for AWG24


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Hi-VHF Square Loop - SWR
Optimum size is 16.75-in for AWG24


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Hi-VHF Square Loop - Impedance
Optimum size is 16.75-in for AWG24


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Ch6 (ONLY) Circular Loop - AWG12
Ch6 Raw Gain is about 3.7 dBi
Optimum size is 48-in Diameter


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Ch6 (ONLY) Circular Loop - AWG12
SWR (300) Under 2.5 on Ch6


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Ch6 (ONLY) Circular Loop - AWG12
Lo-VHF Impedance


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Ch6 (ONLY) Square Loop with AWG12
Ch6 Raw Gain is about 3.4 dBi
Optimum size is 38-in per Side


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Ch6 (ONLY) Square Loop with AWG12
SWR (300-ohms) Under 2.5 on Ch6


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Ch6 (ONLY) Square Loop with AWG12
Lo-VHF Impedance


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Ch3+4 Circular Loop with HICT
Ch3 Raw Gain = 3.5 to 3.9 dBi
Optimum size is 64.5-in Diameter


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Ch3+4 Circular Loop with HICT
Ch3 SWR (300-ohms) = 2.4 to 1.9


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Ch3+4 Circular Loop with HICT
Ch2-6 Impedance


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Ch3+4 Square Loop with HICT
Ch3 Raw Gain = 3.3 to 3.6 dBi
Optimum size is 52.0-in per Side


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Ch3+4 Square Loop with HICT
Ch3 SWR (300-ohms) is Under 2.7


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Ch3+4 Square Loop with HICT
Ch2-6 Impedance


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Ch3 (ONLY) Circular Loop with AWG12
Ch3 Raw Gain = 3.5 to 3.9 dBi
Optimum size is 64.5-in Diameter


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Ch3 (ONLY) Circular Loop with AWG12
Ch3 SWR (300-ohms) is Under 2.4


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Ch3 (ONLY) Circular Loop with AWG12
Ch2-6 Impedance


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Ch3 (ONLY) Square Loop with AWG12
Ch3 Raw Gain = 3.2 to 3.5 dBi
Optimum size is 51.0-in per Side


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Ch3 (ONLY) Square Loop with AWG12
Ch3 SWR (300-ohms) is Under 2.7


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Ch3 (ONLY) Square Loop with AWG12
Ch3 Impedance


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Ch2 (ONLY) Square Loop with AWG12
Ch2 Raw Gain is about 3.3 dBi
Optimum size is 56.5-in per Side


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Ch2 (ONLY) Square Loop with AWG12
SWR (300-ohms) is Under 2.7 on Ch2


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Ch2 (ONLY) Square Loop with AWG12
Impedance on Ch2-6


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DOC55
Hi-VHF Circular Loop
Example 4nec2 file


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DOC56
Hi-VHF Square Loop
Example 4nec2 file


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DOC57
Ch3+4 Circular Loop with HICT
4nec2 File


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DOC58
Ch3+4 Square Loop with HICT
4nec2 File


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DOC59
Ch3 (ONLY) Circular Loop with AWG12
4nec2 File


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Ch3 (ONLY) Square Loop with AWG12
4nec2 File


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  Sign the Guestbook. Displaying 5 of 5 entries.
great info
 - 
jim berk, Fri, 22 Jul 2016 8:55AM
What would be the impedance of a 1/2 wave dipole circularly folded, cut to resonate at the center of Hi-VHF and UHF TV bands (195 MHz & 580 MHz) made with two, horizontally placed, 41" long, 3/8" O.D. soft copper tubing to complete the circle but no touching each other at its ends, so they are 1/4" apart at the opposite gaps? One of the gap serves as the feed point.
 - 
Jarvis, Sun, 10 Mar 2013 7:41PM
Try to remember back: C=pi*D
 - 
holl_ands, Sun, 7 Mar 2010 8:28AM
This is good information but how do you include VHF and UHF in one flat antenna? I've had one up and running since Dec2007.
 - 
Sam Wilson, Sun, 6 Dec 2009 7:01PM
Holl_ands,

What is the overall QICT length to create a circular loop antenna? Did you use a 1" gap on the feedpoint?
 - 
Systems2000, Mon, 19 Oct 2009 11:04AM