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.
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
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