VHF Square & Circular Loops

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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.

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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.

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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. 24850 Visits.

enlarge 0KB, 1024x900 1 Hi-VHF Square Loop - Colorized Gain Red and Green colors in loop are modeling segments.	enlarge 0KB, 837x1024 2 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.	enlarge 0KB, 1024x768 3 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.
enlarge 0KB, 1024x696 4 HiVHF Circular Loops - Raw/Net Gain & SWR Optimum Diameter depends on Element Size.	enlarge 0KB, 1024x696 5 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.	enlarge 0KB, 1024x819 6 Hi-VHF Square Loop - AvgGainTest = 1.0 (Typical for all runs) Verifies 4nec2 generates accurate results.
enlarge 0KB, 1024x700 7 Hi-VHF Square Loop - Raw/Net Gain & SWR Optimum size is 20-in for 1/2-in Type M Copper Tubing.	enlarge 0KB, 1024x748 8 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.	enlarge 0KB, 1024x740 9 Hi-VHF Square Loop vs Folded Dipole Compare SWR vs Element Diameter
enlarge 172KB, 1152x686 10 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	enlarge 202KB, 1152x686 11 Hi-VHF Circular Loop - 23-in QICT Hi-VHF SWR (300-ohms) Under 2.6	enlarge 239KB, 1152x686 12 Hi-VHF Circular Loop - 23-in QICT Hi-VHF Impedance
enlarge 312KB, 1024x1024 13 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 174 MHz	enlarge 317KB, 1024x1024 14 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 198 MHz	enlarge 325KB, 1024x1024 15 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 216 MHz
enlarge 336KB, 1024x1024 16 Hi-VHF Circular Loop - 23-in QICT Circular Polarization Pattern at 174 MHz TV/DTV Signals Follow RHCP Curve (Right Hand Circular Polarization)	enlarge 346KB, 1024x1024 17 Hi-VHF Circular Loop - 23-in QICT Circular Polarization Pattern at 198 MHz TV/DTV Signals Follow RHCP Curve (Right Hand Circular Polarization)	enlarge 351KB, 1024x1024 18 Hi-VHF Circular Loop - 23-in QICT Circular Polarization Pattern at 216 MHz TV/DTV Signals Follow RHCP Curve (Right Hand Circular Polarization)
enlarge 170KB, 1152x686 19 Hi-VHF Circular Loop - 23-in QICT Ch2-13 Raw Gain in FORWARD Direction Below ~70 MHz, Gain is more toward SIDES	enlarge 215KB, 1152x686 20 Hi-VHF Circular Loop - 23-in QICT Ch2-13 SWR (300-ohms) is Excessive on the Lower Channels	enlarge 276KB, 1152x686 21 Hi-VHF Circular Loop - 23-in QICT Ch2-13 Impedance
enlarge 300KB, 1024x1024 22 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 54 MHz	enlarge 301KB, 1024x1024 23 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 84 MHz	enlarge 313KB, 1024x1024 24 Hi-VHF Circular Loop - 23-in QICT Azimuthal Pattern at 96 MHz
enlarge 0KB, 1024x819 25 Hi-VHF Square Loop - Raw Gain Optimum size is 20-in for 1/2-in Type M Copper	enlarge 0KB, 1024x819 26 Hi-VHF Square Loop - SWR Optimum size is 20-in for 1/2-in Type M Copper	enlarge 0KB, 1024x819 27 Hi-VHF Square Loop - Impedance Optimum size is 20-in for 1/2-in Type M Copper
enlarge 0KB, 1024x819 28 Hi-VHF Square Loop - Raw Gain Optimum size is 18.5-in for 1/4-in Copper Tubing	enlarge 0KB, 1024x819 29 Hi-VHF Square Loop - SWR Optimum size is 18.5-in for 1/4-in Copper Tubing	enlarge 0KB, 1024x819 30 Hi-VHF Square Loop - Impedance Optimum size is 18.5-in for 1/4-in Copper Tubing
enlarge 0KB, 1024x819 31 Hi-VHF Square Loop - Raw Gain Optimum size is 16.75-in for AWG24	enlarge 0KB, 1024x819 32 Hi-VHF Square Loop - SWR Optimum size is 16.75-in for AWG24	enlarge 0KB, 1024x819 33 Hi-VHF Square Loop - Impedance Optimum size is 16.75-in for AWG24
enlarge 168KB, 1152x686 34 Ch6 (ONLY) Circular Loop - AWG12 Ch6 Raw Gain is about 3.7 dBi Optimum size is 48-in Diameter	enlarge 211KB, 1152x686 35 Ch6 (ONLY) Circular Loop - AWG12 SWR (300) Under 2.5 on Ch6	enlarge 241KB, 1152x686 36 Ch6 (ONLY) Circular Loop - AWG12 Lo-VHF Impedance
enlarge 176KB, 1152x686 37 Ch6 (ONLY) Square Loop with AWG12 Ch6 Raw Gain is about 3.4 dBi Optimum size is 38-in per Side	enlarge 210KB, 1152x686 38 Ch6 (ONLY) Square Loop with AWG12 SWR (300-ohms) Under 2.5 on Ch6	enlarge 243KB, 1152x686 39 Ch6 (ONLY) Square Loop with AWG12 Lo-VHF Impedance
enlarge 192KB, 1152x701 40 Ch3+4 Circular Loop with HICT Ch3 Raw Gain = 3.5 to 3.9 dBi Optimum size is 64.5-in Diameter	enlarge 234KB, 1152x701 41 Ch3+4 Circular Loop with HICT Ch3 SWR (300-ohms) = 2.4 to 1.9	enlarge 280KB, 1152x701 42 Ch3+4 Circular Loop with HICT Ch2-6 Impedance
enlarge 192KB, 1152x701 43 Ch3+4 Square Loop with HICT Ch3 Raw Gain = 3.3 to 3.6 dBi Optimum size is 52.0-in per Side	enlarge 233KB, 1152x701 44 Ch3+4 Square Loop with HICT Ch3 SWR (300-ohms) is Under 2.7	enlarge 277KB, 1152x701 45 Ch3+4 Square Loop with HICT Ch2-6 Impedance
enlarge 192KB, 1152x701 46 Ch3 (ONLY) Circular Loop with AWG12 Ch3 Raw Gain = 3.5 to 3.9 dBi Optimum size is 64.5-in Diameter	enlarge 234KB, 1152x701 47 Ch3 (ONLY) Circular Loop with AWG12 Ch3 SWR (300-ohms) is Under 2.4	enlarge 272KB, 1152x701 48 Ch3 (ONLY) Circular Loop with AWG12 Ch2-6 Impedance
enlarge 187KB, 1152x701 49 Ch3 (ONLY) Square Loop with AWG12 Ch3 Raw Gain = 3.2 to 3.5 dBi Optimum size is 51.0-in per Side	enlarge 233KB, 1152x701 50 Ch3 (ONLY) Square Loop with AWG12 Ch3 SWR (300-ohms) is Under 2.7	enlarge 276KB, 1152x701 51 Ch3 (ONLY) Square Loop with AWG12 Ch3 Impedance
enlarge 168KB, 1152x678 52 Ch2 (ONLY) Square Loop with AWG12 Ch2 Raw Gain is about 3.3 dBi Optimum size is 56.5-in per Side	enlarge 210KB, 1152x678 53 Ch2 (ONLY) Square Loop with AWG12 SWR (300-ohms) is Under 2.7 on Ch2	enlarge 253KB, 1152x678 54 Ch2 (ONLY) Square Loop with AWG12 Impedance on Ch2-6
enlarge 24KB, 791x1024 55 Hi-VHF Circular Loop Example 4nec2 file	enlarge 23KB, 791x1024 56 Hi-VHF Square Loop Example 4nec2 file	enlarge 25KB, 791x1024 57 Ch3+4 Circular Loop with HICT 4nec2 File
enlarge 24KB, 791x1024 58 Ch3+4 Square Loop with HICT 4nec2 File	enlarge 25KB, 791x1024 59 Ch3 (ONLY) Circular Loop with AWG12 4nec2 File	enlarge 23KB, 791x1024 60 Ch3 (ONLY) Square Loop with AWG12 4nec2 File

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Sign the Guestbook. Displaying 6 of 6 entries.

KC8GQB enjoyed the work that was put into the design work will try to build two of the square for the low and high bands thanks
- Michael Slade, Thu, 14 Mar 2019 4:49PM

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