Envelope-to: dave@picks.force9.co.uk Delivery-date: Sat, 21 May 2005 02:05:34 +0100 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1DZIQn-0006VR-EQ for dave@picks.force9.co.uk; Sat, 21 May 2005 02:05:34 +0100 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1DZIQn-0006VF-8D for dave@picks.force9.co.uk; Sat, 21 May 2005 02:05:33 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1DZIQJ-0001v9-Ol for rs_out_1@blacksheep.org; Sat, 21 May 2005 02:05:03 +0100 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1DZIQJ-0001v0-5o for rsgb_lf_group@blacksheep.org; Sat, 21 May 2005 02:05:03 +0100 Received: from joseph.ncoldns.com ([208.181.178.5] helo=generation.lgisp.net) by relay.thorcom.net with esmtp (Exim 4.43) id 1DZIQH-0006sS-3f for rsgb_lf_group@blacksheep.org; Sat, 21 May 2005 02:05:03 +0100 Received: from p1i5f0 (unknown [204.244.17.71]) by generation.lgisp.net (Postfix) with SMTP id 35A8CB6D73 for <rsgb_lf_group@blacksheep.org>; Fri, 20 May 2005 18:04:47 -0700 (PDT) Message-ID: <00a201c55da1$6f8174c0$6e11f4cc@p1i5f0> From: "Steve McDonald" <jsm@gulfislands.com> To: rsgb_lf_group@blacksheep.org References: <000c01c55a6e$8d82f740$37d0fc3e@l8p8y6> <000d01c55b45$acb45e60$ac068351@w4o8m9> <002f01c55d97$09df4840$8c802ed8@server> Date: Fri, 20 May 2005 18:07:18 -0700 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SPF-Result: relay.thorcom.net: 208.181.178.5 is neither permitted nor denied by domain of gulfislands.com Subject: LF: Re: Loop antenna problem Content-Type: text/html; charset=windows-1252 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SpamFiltered: by PlusNet MXCore (v2.00) Content-transfer-encoding: 8bit <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT face=Arial size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">JB - the pickup loop should not be shielded....just use a piece of wire (any guage...no need for #12)... that the main loop is made from. A single turn, connected across your coax feedline.</DIV> <DIV style="FONT: 10pt arial"> </DIV> <DIV style="FONT: 10pt arial">Steve / VE7SL</DIV> <DIV style="FONT: 10pt arial"> </DIV> <DIV style="FONT: 10pt arial"><BR> </DIV> <DIV><FONT face=Arial size=2>Hello LF Group,</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>I've finally finished the construction of my LF loop and I appear to have a </FONT></DIV> <DIV><FONT face=Arial size=2>problem with it regarding the connection to the receiver. The loop itself</FONT></DIV> <DIV><FONT face=Arial size=2>is in the form of an octagon, with an overall diameter of 10.5 feet, and it</FONT></DIV> <DIV><FONT face=Arial size=2>consists of 15 turns of number 12 THHN stranded wire. The spacing of</FONT></DIV> <DIV><FONT face=Arial size=2>the turns is 0.25 inch and the tuning is done </FONT><FONT face=Arial size=2>with a 3 gang, 400 pF. per</FONT></DIV> <DIV><FONT face=Arial size=2>section, variable capacitor with all sections </FONT><FONT face=Arial size=2>connected in parallel.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>Checking with a weak signal source, the tuning </FONT><FONT face=Arial size=2>range is roughly 100 to</FONT></DIV> <DIV><FONT face=Arial size=2>300 kHz. This agrees with Reg's program for </FONT><FONT face=Arial size=2>multi-turn loop antennas.</FONT></DIV> <DIV><FONT face=Arial size=2>A portable radio covering the LF band really comes to life when I bring</FONT></DIV> <DIV><FONT face=Arial size=2>it close to the loop, and by turning the loop in azimuth I can peak the</FONT></DIV> <DIV><FONT face=Arial size=2>signals and/or null out noise. This would indicate that it is working as</FONT></DIV> <DIV><FONT face=Arial size=2>I would expect.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>The problem is with the pickup loop, which is of the classical shielded</FONT></DIV> <DIV><FONT face=Arial size=2>construction as described in many antenna books. Mine is made from</FONT></DIV> <DIV><FONT face=Arial size=2>RG-213 coax and it's positioned roughly six inches inside of the main</FONT></DIV> <DIV><FONT face=Arial size=2>loop windings, but in the same plane. The station receiver, a TS-440S,</FONT></DIV> <DIV><FONT face=Arial size=2>gets better reception of LF signals when it's connected to my 40 meter</FONT></DIV> <DIV><FONT face=Arial size=2>delta loop than it does with the LF loop!! I know the feedline is OK, as</FONT></DIV> <DIV><FONT face=Arial size=2>I've checked it with an MFJ-259 antenna bridge and a 50 ohm load at</FONT></DIV> <DIV><FONT face=Arial size=2>the </FONT><FONT face=Arial size=2>antenna end.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>The one suspicion I do have is that the cable clamps I've used to hold</FONT></DIV> <DIV><FONT face=Arial size=2>the pickup loop to the frame are made of metal and are shaped like a</FONT></DIV> <DIV><FONT face=Arial size=2>capital letter P. I'm wondering if these look like shorted turns to the</FONT></DIV> <DIV><FONT face=Arial size=2>pickup loop and are attenuating the signal? Before I get out my big</FONT></DIV> <DIV><FONT face=Arial size=2>stepladder and replace them, I thought I'd ask the opinions of those</FONT></DIV> <DIV><FONT face=Arial size=2>of you </FONT><FONT face=Arial size=2>who have gone before me. Any/all suggestions are welcome.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>73, J.B. Weazle McCreath, VE3EAR - VE3WZL</FONT></DIV> <DIV> </DIV></BLOCKQUOTE></BODY></HTML>