Return-Path: <majordom@post.thorcom.com> Received: (qmail 16143 invoked from network); 15 Sep 1999 18:48:51 +0100 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 15 Sep 1999 18:48:51 +0100 Received: (qmail 1760 invoked from network); 15 Sep 1999 17:52:56 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by magnet.plus.net.uk with SMTP; 15 Sep 1999 17:52:56 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11RIcI-0004jt-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 15 Sep 1999 18:13:10 +0100 Received: from [143.179.236.31] (helo=Iguanodon.big-orange.net) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11RIcF-0004jo-00 for rsgb_lf_group@blacksheep.org; Wed, 15 Sep 1999 18:13:07 +0100 Received: from w8k3f0 ([143.179.150.53]) by Iguanodon.big-orange.net (Netscape Messaging Server 3.6) with SMTP id AAA5F50; Wed, 15 Sep 1999 19:13:00 +0200 Message-ID: <000d01beff9e$9ff064c0$3596b38f@w8k3f0> From: "Dick Rollema" <d.w.rollema@gironet.nl> To: "LF-Group" <rsgb_lf_group@blacksheep.org> Cc: "Koos Fockens, PA0KDF" <kfockens@worldonline.nl> Subject: LF: LF-antenna with top load Date: Wed, 15 Sep 1999 19:19:49 +0200 MIME-Version: 1.0 Content-Type: text/html; charset=windows-1252 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: <majordom@post.thorcom.com> Content-transfer-encoding: 8bit <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=text/html;charset=iso-8859-1 http-equiv=Content-Type><!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"><!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <META content='"MSHTML 4.72.3110.7"' name=GENERATOR> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT color=#000000 face=Courier>To All</FONT></DIV> <DIV><FONT color=#000000 face=Courier></FONT> </DIV> <DIV><FONT color=#000000 face=Courier>As there has been some discussion on the merits of different kinds of top</FONT></DIV> <DIV><FONT color=#000000 face=Courier>loading I have performed some computer simulation, using the Antenna Optimizer program by Brian Beezley, K6STI, which is similar to EZNEC.</FONT></DIV> <DIV><FONT color=#000000 face=Courier></FONT> </DIV> <DIV><FONT color=#000000 face=Courier>The program computes the impedance in the feed point over a perfect ground. This means that in the real world the radiation resistance will be somewhat different, but for comparison purposes (what is better, what is worse) the computed values can be used very well. </FONT></DIV> <DIV><FONT color=#000000 face=Courier></FONT> </DIV> <DIV><FONT color=#000000 face=Courier>The loss due to the resistance of the wires is taken into account and efficiency is calculated as the radiation resistance divided by the total resistance (radiation resistance </FONT><FONT color=#000000 face=Courier>+ ohmic loss in the wire). In the real situation the loss in the loading coil and the earth resistance have to be added. </FONT></DIV> <DIV><FONT color=#000000 face=Courier></FONT><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>The goal is of course to make the <U>radiation resistance as high as possible</U>. A large capacitance helps as well because the loading coil - and thus its loss (X/Q) - becomes smaller. But in the majority of cases the earth resistance forms the largest</FONT></DIV> <DIV><FONT face=Courier>component of the total resistance so the effect of the smaller loss in the coil is diluted by the unchanged earth resistance.</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT color=#000000 face=Courier>As many amateurs seem to be restricted to a height of about 10 metres I have used a vertical radiator of 10 m for all cases. The antenna is fed at the bottom of the radiator.</FONT></DIV> <DIV><FONT color=#000000 face=Courier>I assumed the vertical part and top loading wires to be made of 1.5 mm copper wire (16 SWG).</FONT></DIV> <DIV><FONT color=#000000 face=Courier></FONT> </DIV> <DIV><FONT color=#000000 face=Courier><STRONG>1. No top load</STRONG></FONT></DIV> <DIV><FONT color=#000000 face=Courier><STRONG></STRONG></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.073 - j 17792 (ohm)</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 10.8%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 7.8 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 65.2 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>2. One horizontal top load wire of 5 m</FONT></STRONG></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.111 - j 12550</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#000000>Efficiency: 12.5%</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 13.9 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 92.5 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>3. One top loading wire of 5 m, sloping down under 45 degrees</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.108 - j 12993</FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 10.4%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 11.2 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 89.3 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>4. One horizontal top loading wire of 10 m</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.148 - j 9659</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 11.9%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 17.6 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 120 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>5. One top loading wire of 10 m, sloping down under 45 degrees</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.142 - j 9898 </FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 7.0%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 9.94 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 117 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>6. One horizontal top loading wire of 20 m</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.221 - j 6626</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 10.0%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 22.1 milli-ohm</FONT></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 175 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>7. Two horizontal top loading wires of 5 m (T-antenna)</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.133 - j 9914</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 13.1%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 17.4 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 117 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>8. Two top loading wires of 5 m, sloping down under 45 degrees</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.127 - j 10466</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 10.4%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 13.2 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 111 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>9. Two horizontal top loading wires of 10 m (T-antenna)</FONT></STRONG></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.173 - 6793</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 12.7%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 22.0 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 171 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>10. Two top loading wires of 10 m, sloping down under 45 degrees</FONT></STRONG></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.163 - j 6987</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 6.5%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 10.6 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 166 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>11. Two horizontal top loading wires of 20 m (T-antenna)</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.230 - j 4142</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 11.3%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 26.0 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 280 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>12. Four horizontal top loading wires of 5 m (90 degrees between wires in horizontal plane)</FONT></STRONG></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.156 - j 7394</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 13.7%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 21.4 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 157 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>13. Four top loading wires of 5 m, sloping down under 45 degrees</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.147 - j 7948</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 10.1%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 14.9 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 146 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>14. Four horizontal top loading wires of 10 m</FONT></STRONG></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.193 - j 4529</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 13.4%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 25.9 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 256 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><STRONG>15. Four top loading wires of 10 m, sloping down under 45 degrees</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.180 - j 4689</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 6.0%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 10.8 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 247 pF</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><STRONG>16. Four horizontal toploading wires of 20 m (T-antenna)</STRONG></FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Z = 0.232 - j 2493</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier>Efficiency: 12.5%</FONT></DIV> <DIV><FONT face=Courier></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>Rs: 29 milli-ohm</FONT></FONT><FONT color=#ff0000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT><FONT color=#ff0000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#ff0000>C: 466 pF</FONT></FONT></DIV> <DIV><FONT face=Courier><FONT color=#ff0000></FONT></FONT> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><FONT color=#000000>The detrimental effect of downward sloping wires is evident, especially when the ends come near the ground (cases 5, 10 and 15).</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV> </DIV> <DIV> </DIV> <DIV><FONT face=Courier><FONT color=#000000>73, Dick, PA0SE</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000></FONT></FONT><FONT color=#000000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#000000>D.W. Rollema</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000>V.D. Marckstraat 5</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000>2352 RA Leiderdorp</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000>The Netherlands</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000>Tel. +31 71 589 27 34</FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000>E-mail: <A href="mailto:d.w.rollema@gironet.nl">d.w.rollema@gironet.nl</A></FONT></FONT><FONT color=#000000></FONT></DIV> <DIV><FONT face=Courier><FONT color=#000000></FONT></FONT><FONT color=#000000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#000000></FONT></FONT><FONT color=#000000></FONT> </DIV> <DIV><FONT color=#000000></FONT> </DIV> <DIV><FONT face=Courier><FONT color=#000000></FONT></FONT><FONT color=#000000> </FONT></DIV> <DIV> </DIV> <DIV><FONT face=Courier></FONT> </DIV></BODY></HTML>