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92 lines
6.8 KiB
HTML
92 lines
6.8 KiB
HTML
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<title>All-Band Use of Horizontal-Plane Loops</title>
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<h1><img src="../images/wirecad.gif" align="middle" width="125" height="62" border="2" vspace="5" hspace="9"> Notes on All-Band Use of Horizontal-Plane Loops <img src="../images/w4rnlwwr.gif" align="middle" width="99" height="83" border="2" vspace="5" hspace="10"></h1>
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<h3>L. B. Cebik, W4RNL</h3>
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To set a contrast with the vertical-plane (VP) loops (covered in another note in this series on vertical-plane deltas), I made a couple of models of 80- meter 4-sided horizontal-plane (HP) loops, each 70' per side to bring them close to resonance in the 80-meter band. One I fed at a corner; the other a fed mid-side. The loops are at 35' up over medium earth and are #12 copper wire.
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<img src="hl7.gif" width="497" height="280" border="2" vspace="5" hspace="9">
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<p>The general summary is this: on 80, either loop is a cloud burner, but with pretty good gain at 45 degrees elevation. In general, except for 40 meters, the corner-fed loop shows more bi-directional patterns (with minor side lobes), mostly through the corners where the feedpoint is the backside. On bands from 20 meters, there is up a slight (3-4 dB) front-to-back ratio.</p>
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<p>Fed on one side (rather than at a corner), there is a tendency for the antenna to exhibit more lobes per band, with those to the far side from the feedpoint being slightly stronger--again by no more than 2-4 dB.</p>
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<p>Both the corner-fed and the side-fed antennas, as the charts will show, represent easy work on an antenna tuner, with very reasonable values of R and X. Indeed, a 300- ohm line will likely show the smallest excursions of R and X along the line length, although 450-ohm line is perfectly good as well. From the values in the chart, line length should not be critical.</p>
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<p>In the charts below, all maximum gain figures use the TO angle (elevation angle of maximum radiation) except for 80 meters, whether the gain is at a 45-degree TO angle.</p>
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<pre>1 wl loop (70'/side), corner-fed: #12 copper 35' up over medium earth:
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Freq. TO angle Max Gain Feed Z Pattern notes
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MHz degrees dBi R+/-jX
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3.58 90 5.16@45 67 +j 4 oval thru corners
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7.1 48 5.69 84 -j150 oval across corners
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10.1 41 9.32 370 -j575 narrow oval thru corners
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14.1 27 10.51 305 -j105 clover leaves thru corners
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18.1 20 13.75 350 +j240 EDZ-like thru corners
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21.1 17 13.63 245 -j105 clover
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24.95 14 14.09 320 +j110 thru crnrs w/side lobes
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28.1 12 12.92 225 -j145 12 lobes
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1 wl loop (70'/side, side-fed:) #12 copper 35' up over medium earth:
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Freq. TO angle Max Gain Feed Z Pattern notes
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MHz degrees dBi R+/-jX
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3.58 90 5.09@45 65 +j 4 oval thru sides
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7.1 44 6.73 275 +j130 oval thru sides
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10.1 35 6.86 285 -j535 lobes at corners
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14.1 27 9.69 265 -j165 4 lobes at corners
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18.1 21 11.65 400 +j180 6 lobes, strong=far side
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21.1 18 10.61 400 -j120 many lobes, strng=far side
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24.95 15 11.08 370 +j 45 many lobes, strng=far side
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28.1 11 11.83 250 -j180 many lobes, strng=far side</pre>
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<p>The side-fed shows slightly less max gain on the upper bands, but has more stronger lobes other than the corner-fed version. If the pattern notes can be deciphered, you can choose whichever suits your operating desires most.</p>
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<p>To assiset in interpreting the brief pattern notes, the following azimuth patterns of corner-fed and side-fed HP loops at 10.1, 21.1, and 28.1 MHz may be useful. For each pattern, the antenna is a square aligned with the graphic borders. The corner-fed model is fed at the lower left corner of the graphic. The side-fed model is fed at the middle of the left side.</p>
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<img src="hl1.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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<img src="hl2.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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<p>The 10.1 MHz patterns show the most unique differences, with the corner-fed model having a beam-like pattern, while the side-fed model pattern is somewhat non-descript but more omni-directional.</p>
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<img src="hl3.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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<img src="hl4.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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<p>At 21.1 MHz, the side-fed model shows much broader lobes, while the energy from the corner-fed model is concentrated in 4 fairly narrow lobes.</p>
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<img src="hl5.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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<img src="hl6.gif" width="640" height="480" border="2" vspace="5" hspace="9">
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</center>
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<p>By the 10 meter band, there is little to choose from between the two antennas.</p>
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<p>As a general rule, the horizontal loop offers more directions, especially in the side-fed version, than the single wire, which concentrates its energy more toward the ends as the frequency goes up. A compendium of patterns for 135' doublets and for 102' doublets appears in notes taken from the series done for <i>Low Down</i>. The loop has fewer bands with problematical impedances than any of the doublets.</p>
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<p>For all-band use, the HP loop seems to offer more than the VP loop. The HP loop elevation angles are close to those of a single wire doublet, which places them lower and stronger than those for a VP loop. In general, with either mode of feeding, expect strongest results in the quadrants across the way from the feedpoint.<br>
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<br></p>
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<p><i>Updated 10-28-97. © L. B. Cebik, W4RNL. Data may be used for personal purposes, but may not be reproduced for publication in print or any other medium without permission of the author.</i><br>
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<br></p>
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<a href="../radio.html"><img src="../images/return.gif" align="bottom" width="40" height="40"> Go to Amateur Radio Page</a><br>
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<p class="topics-footer">Topics: <a href='../topics.html#hf-multi-band'>HF Multi Band</a>, <a href='../topics.html#horizontal-loop'>Horizontal Loop</a></p><br>
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