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</o:shapelayout></xml><![endif]--></head><body lang=PT link=blue vlink=purple><div class=WordSection1><div align=center><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0 width=990 style='width:594.0pt'><tr><td width=10 style='width:6.0pt;padding:0cm 0cm 0cm 0cm'></td><td width=610 valign=top style='width:366.0pt;padding:0cm 0cm 0cm 0cm'><table class=MsoNormalTable border=0 cellspacing=0 cellpadding=0 width=610 style='width:366.0pt'><tr><td style='padding:0cm 0cm 0cm 0cm'></td></tr><tr style='height:6.0pt'><td style='padding:0cm 0cm 0cm 0cm;height:6.0pt'></td></tr><tr><td style='padding:0cm 0cm 0cm 0cm'><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='font-size:13.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Simple Loop Antennas <br></span></b><b><span lang=EN-US style='font-size:10.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>by G0FTD<br>Updated 5 Nov 2011</span></b><b><span lang=EN-US style='font-size:13.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><o:p></o:p></span></b></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Several years ago I wrote a short article about my experiences in using very simple wire loop antennas for discrete use. I have now decided to give it a little update.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>It all started when I found myself away from home and often abroad through my employment and wishing to use some of my amateur radio equipment from the various hotels or bed and breakfasts I stayed at.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>My employment WAS in designing antennas afterall, so it was about time<br>I used the experience for my own requirements!<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>My experience has shown if you have to use an indoor antenna it's probably best to use some kind of loop as opposed to a simple vertical or end fed system. Not sure why, but it just seems to be the case, especially when trying to use the LF bands. I have also found a preference for making loops standing vertical as opposed to horizontal.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Loop Version 1</span></b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>This simple loop antenna was in use by me for several years in various<br>QTH's. You start by taking a basic square loop of approximatley 2.4m<br>long for each side. You feed it at the bottom centre, via a 1:1 balun<br>and a T-Match ATU.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>THE 1:1 balun I found to be of great assistance when using extremely compact stations in reducing noise on receive and RF flowing other station cabling.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>The latter sometimes manifests itself with RF bites when touching equipment, varying SWR when touching equipment, or RF on cables connecting PC equipment to radio equipment. WARNING! This is a common problem with all stations or unbalanced antenna systems. I've damaged computer equipment in the past, so ALWAYS do some basic checks first before applying more than about 10 watts.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>You will note that I also specified a T Match ATU. A T Match will provide<br>a much greater range of impedance matching as opposed to something like a Pi or L match system.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Both the balun and ATU MUST be used actually at the feed point of the <br>loop, and never ever at the rig end. If you try the latter you will get<br>a reduction in performance.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>At the top centre of the loop you may put a simple open/close switch.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>This can be used on 10/12m to alter the polar pattern by 90 degrees.<br>In other words, you are able to rotate the beam of the antenna around without actually moving the antenna! It also switches that radiation from vertical to horizontal.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>This loop can be used from 160m - 6m. I have rarely used more than 15w<br>and had massive success especially from 30m upwards. <o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>What have I worked ?<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>The world! Right down to VK land, South Africa and South America.<br>On 6m I've never used more than 5w and I seem to work just as many <br>stations as anyone else during the summer sporadic E season.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>On the LF bands performance is reduced, but I have worked the <br>Ukraine on 80m, Cyprus on WSPR and regular QSO's on 3.560Mhz CW<br>on the QRP frequency at night.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>I've made a few local QSO's on 160m,about 30 miles away but I've never<br>made too much effort on that band using this small loop.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><img width=762 height=250 id="Imagem_x0020_4" src="cid:image001.jpg@01CC9D40.F502A200" alt="Descrição: http://www.southgatearc.org/articles/g0ftd/loop_antennas/images/diagram.gif"></span><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'> <o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><img width=762 height=341 id="Imagem_x0020_5" src="cid:image002.jpg@01CC9D40.F502A200" alt="Descrição: http://www.southgatearc.org/articles/g0ftd/loop_antennas/images/compare.jpg"></span><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'> <o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Loop Version 2 </span></b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><br><br>In an attempt to improve LF performance I tried a large loop.<br>This was approximately 4.2m x 2.4m and fed in the corner. Again the use of a balun and T Match atu is essential. This seemed to give a useful performance boost on the LF bands, and works well up to 6m.<br>The radiation pattern is pretty omnidirectional at LF, moving to bi-directional on the upper HF bands, and then on 6m it becomes a four lobed system offering about 2db gain over a dipole.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'> <o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Using an Indoor Station</span></b><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'><o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>I originally wanted to use these loops purely for indoor use, and I've had a lot of fun with them over the years. <o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>Naturally you cannot expect to be as big a signal as others, but that doesn't stop you working DX.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>I usually find CW scores over SSB, and now there's modes like PSK31<br>and WSPR. The latter mode is an indoor QRP'ers delight and I thoroughly<br>recommend it.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>So if you are a flat dweller, have no garden or live in a broom cupboard<br>this proves that the HF bands ARE available to you.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-US style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>So now the sunspots are up - get cracking and have some fun.<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style='font-size:12.0pt;font-family:"Verdana","sans-serif";mso-fareast-language:PT'>73 de <br><b><i>Andy G0FTD</i></b><o:p></o:p></span></p></td></tr></table></td></tr></table></div><p class=MsoNormal><o:p> </o:p></p></div></body></html>