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AMfone's Online AM Handbook => Antennas => Topic started by: Steve - K4HX on February 02, 2012, 10:42:16 PM



Title: 10 Meter Rectangular Loop
Post by: Steve - K4HX on February 02, 2012, 10:42:16 PM
Here is a very simple wire antenna you can build for 10 meters and quickly get in on the AM action now that the sunspots have returned. It is nothing more than a rectangular full-wave loop that has a 2:1 height-to-width ratio. It is fed at the bottom-middle of the loop and the feedpoint impedance is 50 Ohms.

(http://www.amwindow.org/misc/10mloop/10mrectloop.gif)


The dimensions above are for uninsulated wire and will produce resonance at the lower end of the 10 meter band. I built a loop using 36 feet of #12 insulated wire and had to trim 8-10 inches to obtain resonance at around 28.8 MHz (better for AM operation above 29 MHz). If I had to do it over, I would have made the loop 35 feet in total length and put a 6 inch stub with a shorting bar at the top of the loop (opposite the feedpoint). Sliding the shorting bar would allow for setting the center frequency almost anywhere in the band quickly and easily.

(http://www.amwindow.org/misc/10mloop/10mrectloop.jpg)


The antenna can be put aloft with just one support. I used a rope and PVC horizontal spreaders/spacers (as shown in the photo above) or you could mast mount the loop (as shown in the drawing below). PVC pipe can be used as spreaders or support arms.

(http://www.amwindow.org/misc/10mloop/mast4loop.gif)


The loop has 1-2 dB more gain than a horizontal dipole and 8 db gain over a vertical dipole (or most other verticals). It still has broad lobes like a dipole, so geographic coverage is good. If mast mounted, a rotor could be used. I turn mine (tree mounted) with a rope.

Loop Versus Horizontal Dipole (loop pattern in Red)

(http://www.amwindow.org/misc/10mloop/10mrectloopvsdipaz.gif)
Azimuth


(http://www.amwindow.org/misc/10mloop/10mrectloopvsdipel.gif)
Elevation


Loop Versus Vertical Dipole (loop pattern in Red)

(http://www.amwindow.org/misc/10mloop/10mrectloopvsvertaz.gif)
Azimuth


(http://www.amwindow.org/misc/10mloop/10mrectloopvsvertel.gif)
Elevation


Make sure you use a balun at the feedpoint. Several turns of coax in an 8 inch loop will work fine or you can use a bead or toroid balun.

If you want to get on 10 meters and join in the fun, try this rectangular loop. You can build it and have it up and on the air in an afternoon.

Catch you on 10!


Title: Re: 10 Meter Rectangular Loop
Post by: KA3VID on November 03, 2021, 09:25:56 PM
Since it's all I have on hand would 450 ohm ladderline work with this antenna, or do you only recommend using coax ?
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