Return-Path: Received: from rly-mf07.mx.aol.com (rly-mf07.mail.aol.com [172.20.29.177]) by air-mf03.mail.aol.com (v123.4) with ESMTP id MAILINMF032-96e4a09770678; Tue, 12 May 2009 09:18:11 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-mf07.mx.aol.com (v123.4) with ESMTP id MAILRELAYINMF074-96e4a09770678; Tue, 12 May 2009 09:18:02 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M3rqj-00031P-0N for rs_out_1@blacksheep.org; Tue, 12 May 2009 14:16:49 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M3rqi-00031G-9W for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 14:16:48 +0100 Received: from mail-bw0-f171.google.com ([209.85.218.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M3rqf-0007hc-0X for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 14:16:47 +0100 Received: by bwz19 with SMTP id 19so4287660bwz.4 for ; Tue, 12 May 2009 06:16:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=1rer1/RPHU1CY39n+3VenGdNcQnmgCGzgUV/HFhBFp0=; b=Tcx6sl6sRfZb/BF0z/Ij4iCAXPy1blAs1YoVMbWNmFmfIhrY5be5eGEdZ0wWUswP+J wj6xNJR6xc0HvQ9gt9b8ig0ggSsxJlDVmPaWmAHcsvbJjftBH9B/prAslYzJGZQg8Kc9 XWOYupwDqwOuXnYvHNDVKXS4jQhjoTe1GJtPA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=hRuKjm8lVDgyMviQSs8rIzg/NXwbBhv/yS2U33qEbY1qIDDCVr2cuKNgJznxZSMeCo K9sg3Sv/ToQFT8Tis+54cc/vJP0v8RYZSEyoJv/aDlLznVjxuGOy5n3WmJutFMS/zHyG uO0i6KQU2Q3imQ2D3t9chBEusEvMZ1SApLLWU= MIME-Version: 1.0 Received: by 10.204.117.203 with SMTP id s11mr8023949bkq.153.1242134198872; Tue, 12 May 2009 06:16:38 -0700 (PDT) In-Reply-To: <007401c9d2fa$863a6280$0301a8c0@mal769a60aa920> References: <4A01AEA0.1030308@btconnect.com> <003801c9cfed$3754c170$0301a8c0@mal769a60aa920> <4A094F88.31094.2E46CD4@mike.dennison.ntlworld.com> <007401c9d2fa$863a6280$0301a8c0@mal769a60aa920> Date: Tue, 12 May 2009 14:16:38 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Karma: unknown: DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: Re: 500kHz Portable Content-Type: multipart/alternative; boundary=0016e6d64865afea890469b6e724 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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 X-AOL-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d251.1 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --0016e6d64865afea890469b6e724 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit A full quarter wave inverted L with sloping end is starting to become a loop with the ground path forming part of the loop conductor, rather than a vertical. ANY antenna that approaches more than about a tenth of a wavelength cannot be treated as small any more, and must be considered in its entirety. Such is obvious even before resorting to modelling. Mike was referring to electrically short antennas where the downward sloping part simply opposes the current flow in the upward path. A small amount of slope on a large capacity hat might not be too noticeable in practice, as a lot of extra capacitance at the top could do more good than its slope undoes. Please stop and actually think, and perhaps before being so rude and treating all why don't own millions of hectares of farmland as second-class radio-ams, you stop and read the exam question. Andy G4JNT wobbleU cubed .g4jnt.kom 2009/5/12 mal hamilton > You are certainly NO EXPERT at amateur radio never mind LF/MF and > especially antennas. > I have worked the world on LF/MF using Inv L antennas with the far end just > above ground , and in normal CW mode. > Some time ago it was Comics, elevated lemonade bottles as coil formers, > thought an AR88D was a diversity fly catcher. > What is coming next? The diversity UMBRELLA!!!! > My current MF antenna is a full 1/4 wave inv L, 100 ft high and performs > well but for some this might be difficult, therefore use what you can get on > your property and let the far end tilt down if necessary. > G3KEV > > ----- Original Message ----- From: "Mike Dennison" < > mike.dennison@ntlworld.com> > To: > Sent: Tuesday, May 12, 2009 10:29 AM > Subject: Re: LF: Re: Re: 500kHz Portable > > > You do not need 2 masts for an inv L or T antenna. >>> The so called horizontal wire(s) can slope down and the far end tied >>> to a bush or tree, or a stake in the ground via an insulator, as far >>> away as possible from the vert section, the longer the better. Keep it >>> simple. mal/g3kev >>> >> >> This is quite wrong. Any slope downwards will reduce the effective >> height of a Marconi. Since ERP is a function of the square of the >> effective height this is extremely important. An umbrella is far >> preferable to an inverted-L in a single mast situation because a >> large amount of capacitance to ground can be achieved without much >> reduction of effective height. >> >> Based on my experience of LF portable (both on 73 and 136kHz), my >> advice is to make very sure that the remote ends of a Marconi are >> very well insulated as they carry large voltages. Keep well away from >> wet trees. This is not just a safety issue; any voltage leaked is >> power lost. >> >> Mike, G3XDV >> ========== >> >> >> > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.325 / Virus Database: 270.12.25/2109 - Release Date: 05/11/09 > 16:14:00 > > > --0016e6d64865afea890469b6e724 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
A full quarter wave inverted L with sloping end is starting to become a= loop with the ground path forming part of the loop conductor, rather than a= vertical.=A0=A0 ANY antenna that approaches more than about a tenth of a wa= velength cannot be treated as small any more, and must be considered in its=20= entirety.=A0 Such is obvious even before resorting to modelling.=A0 Mike was= referring to electrically short antennas where the downward sloping part si= mply opposes the current flow in the upward path.=A0=A0=A0
=A0
A small amount of slope on a large capacity hat might not be too notice= able in practice, as a lot of extra capacitance at the top could do more goo= d than its slope undoes.
=A0
Please stop and actually think, and perhaps before being so rude and= =A0treating all why don't own millions of hectares of farmland as second= -class radio-ams, you stop and read the exam question.

Andy =A0G4JNT
wobbleU cubed .g4jnt.kom


=
2009/5/12 mal hamilton <g3kevmal@talktalk.net>
You are certainly NO EXPERT at ama= teur radio never mind LF/MF and especially antennas.
I have worked the wo= rld on LF/MF using Inv L antennas with the far end just above ground , and i= n normal CW mode.
Some time ago it was Comics, elevated lemonade bottles as coil =A0formers, t= hought an AR88D was a =A0diversity fly catcher.
What is coming next? The=20= diversity UMBRELLA!!!!
My current MF antenna is a full 1/4 wave inv L, 10= 0 ft high and performs well but for some this might be difficult, therefore=20= use what you can get on your property and let the far end tilt down if neces= sary.
G3KEV

----- Original Message ----- From: "Mike Dennison" &l= t;mike.denni= son@ntlworld.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, May 12, 2009 10:29 AM
Subject: Re: LF: Re: Re: 500kHz Port= able


You do not need 2 masts for an inv= L or T antenna.
The so called horizontal wire(s) can slope down and the=20= far end tied
to a bush or tree, or a stake in the ground via an insulator, as far
away= as possible from the vert section, the longer the better. Keep it
simple= . mal/g3kev

This is quite wrong. Any slope downwards wil= l reduce the effective
height of a Marconi. Since ERP is a function of the square of the
effecti= ve height this is extremely important. An umbrella is far
preferable to a= n inverted-L in a single mast situation because a
large amount of capacit= ance to ground can be achieved without much
reduction of effective height.

Based on my experience of LF portable=20= (both on 73 and 136kHz), my
advice is to make very sure that the remote e= nds of a Marconi are
very well insulated as they carry large voltages. Ke= ep well away from
wet trees. This is not just a safety issue; any voltage leaked is
power l= ost.

Mike, G3XDV
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D




--------------------------------------------------------------= ------------------



No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8= .5.325 / Virus Database: 270.12.25/2109 - Release Date: 05/11/09 16:14:00


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