X-GM-THRID: 1201186422343445523 X-Gmail-Labels: rsgb lf X-Gmail-Received: 542efaae93722d345c5bc7a411e85207a4bfda15 Delivered-To: daveyxm@gmail.com Received: by 10.54.70.6 with SMTP id s6cs18551wra; Thu, 20 Apr 2006 06:44:00 -0700 (PDT) Received: by 10.49.88.12 with SMTP id q12mr430852nfl; Thu, 20 Apr 2006 06:43:59 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.gmail.com with ESMTP id a23si871468nfc.2006.04.20.06.43.59; Thu, 20 Apr 2006 06:43:59 -0700 (PDT) Received-SPF: neutral (gmail.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1FWZNo-0005RP-T9 for rs_out_1@blacksheep.org; Thu, 20 Apr 2006 14:39:44 +0100 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1FWZNo-0005RG-39 for rsgb_lf_group@blacksheep.org; Thu, 20 Apr 2006 14:39:44 +0100 Received: from hestia.herts.ac.uk ([147.197.200.9]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1FWahf-0001Cr-P1 for rsgb_lf_group@blacksheep.org; Thu, 20 Apr 2006 16:04:21 +0100 Received: from [147.197.215.113] (helo=tucana.herts.ac.uk) by hestia.herts.ac.uk with esmtp (Exim 3.22 #1) id 1FWZN0-0006ON-00 for rsgb_lf_group@blacksheep.org; Thu, 20 Apr 2006 14:38:54 +0100 Received: from [147.197.164.230] (helo=RD40002) by tucana.herts.ac.uk with esmtp (Exim 4.44) id 1FWZMy-0004Iw-Pp for rsgb_lf_group@blacksheep.org; Thu, 20 Apr 2006 14:38:52 +0100 From: "james moritz" To: Date: Thu, 20 Apr 2006 14:38:51 +0100 Message-ID: <000001c6647f$c2daa110$e6a4c593@RD40002> MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal In-Reply-To: <6.1.0.6.2.20060420110722.0363be90@127.0.0.1> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 X-UH-MailScanner: No Virus detected X-UH-MailScanner-Information: X-H-UH-MailScanner: No Virus detected X-UH-MailScanner-From: j.r.moritz@herts.ac.uk X-Spam-Score: -1.0 (-) X-Spam-Report: autolearn=disabled,AWL=-1.072,HTML_50_60=0.095,HTML_MESSAGE=0.001 Subject: LF: RE: Top load coil at ground level? Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C66488.249F0910" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40, HTML_FONTCOLOR_UNKNOWN,HTML_MESSAGE autolearn=no version=2.63 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 Status: O X-Status: X-Keywords: X-UID: 5601 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C66488.249F0910 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Dear Dick, LF Group, =20 I am puzzled as to how the top-loaded vertical antenna plus stub is = supposed to operate. In Fig 1, the elevated loading coil is in series between the vertical element and the top loading, which is perfectly reasonable - = but I can't see how the stub in Fig 2 could produce an equivalent series = inductive reactance, especially since one terminal of the stub is unconnected. =20 I can see that Dex's antenna works (I presume the arrangement in Section 2.12 of ON7YD's antennas page), but I don't think it is equivalent to an elevated loading coil. The vertical wire from the hot end of the loading coil to the top loading section will be at high voltage along its whole length, leading to much the same displacement currents flowing to ground = and in the mast, and therefore the same current distribution, as would occur with a conventional inverted-L with a ground-level loading coil. This contrasts with a top-loaded vertical with elevated loading coil at the = top of the vertical section, where all the vertical part of the antenna is = at low RF potential, and only the top loading section carries a high RF voltage. The main effect of using the mast and the additional vertical = wire from the top of the mast to the cold end of the loading coil as part of = the antenna system would seem to be to add their distributed inductance to = the cold end of the loading coil. In other words, you would achieve an = almost identical result by grounding the cold end of the loading coil to the = bottom of the mast, and adding some extra turns to the cold end of the loading coil. =20 Cheers, Jim Moritz 73 de M0BMU =20 ------=_NextPart_000_0001_01C66488.249F0910 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Dear Dick, LF = Group,

 

I am puzzled as to how the = top-loaded vertical antenna plus stub is supposed to operate. In Fig 1, the = elevated loading coil is in series between the vertical element and the top = loading, which is perfectly reasonable – but I can’t see how the stub = in Fig 2 could produce an equivalent series inductive reactance, especially = since one terminal of the stub is unconnected.

 

I can see that Dex’s antenna = works (I presume the arrangement in Section 2.12 of ON7YD’s antennas page), = but I don’t think it is equivalent to an elevated loading coil. The = vertical wire from the hot end of the loading coil to the top loading section = will be at high voltage along its whole length, leading to much the same = displacement currents flowing to ground and in the mast, and therefore the same current = distribution, as would occur with a conventional inverted-L with a ground-level = loading coil. This contrasts with a top-loaded vertical with elevated loading coil at = the top of the vertical section, where all the vertical part of the antenna is = at low RF potential, and only the top loading section carries a high RF = voltage. The main effect of using the mast and the additional vertical wire from the top = of the mast to the cold end of the loading coil as part of the antenna system = would seem to be to add their distributed inductance to the cold end of the = loading coil. In other words, you would achieve an almost identical result by = grounding the cold end of the loading coil to the bottom of the mast, and adding = some extra turns to the cold end of the loading coil.

 

Cheers, Jim = Moritz

73 de M0BMU

 

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