Return-Path: Received: from rly-db02.mx.aol.com (rly-db02.mail.aol.com [172.19.130.77]) by air-db07.mail.aol.com (v123.4) with ESMTP id MAILINDB073-aab4a0bdd5f50; Thu, 14 May 2009 04:59:19 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-db02.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDB021-aab4a0bdd5f50; Thu, 14 May 2009 04:59:14 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M4WlD-00045u-Gx for rs_out_1@blacksheep.org; Thu, 14 May 2009 09:57:51 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M4WlC-00045l-MK for rsgb_lf_group@blacksheep.org; Thu, 14 May 2009 09:57:50 +0100 Received: from mail-gx0-f170.google.com ([209.85.217.170]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M4WlA-0003j0-4E for rsgb_lf_group@blacksheep.org; Thu, 14 May 2009 09:57:50 +0100 Received: by gxk18 with SMTP id 18so1998766gxk.4 for ; Thu, 14 May 2009 01:57:42 -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=9SUzFzAvjhcaqHazGz2UpWfduiKmr7GKHmtp4+XfXJA=; b=B+PBrg0q3PChsS+UmLRePpxQuC+x5xZNsiakaxq4vS/tTD22PCznU0MTkJOiBbyJ8Y GY9tdwin3nsod2rmhawwCY3nfYzHnzOFKQg1B6/Kth2rs/ZousUC1eh7VMRnK5Trd3pX pj+BFEfrnbN+CiWQYTuhUX0V7/kQ5l5YtYnVs= 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=SknXZkpTOG6AJd3s+j8FKKWvjfoNMOydNj5HhUYSrQj3MfhqGaJgwvL5VPD/srEQIm aamxVl1LnxbKI3QLSE+LORF4w/6xvPT6kuQPPhEned/8mvxC9/YtABkoWxr81R1LLEm8 CYL3f4zjz3qyg62q0h+UCDF5/kRn5Y+IgjOb0= MIME-Version: 1.0 Received: by 10.151.133.12 with SMTP id k12mr3189215ybn.168.1242291461980; Thu, 14 May 2009 01:57:41 -0700 (PDT) In-Reply-To: <00ce01c9d327$0f3bc390$0301a8c0@mal769a60aa920> References: <4A01AEA0.1030308@btconnect.com> <003801c9cfed$3754c170$0301a8c0@mal769a60aa920> <4A094F88.31094.2E46CD4@mike.dennison.ntlworld.com> <007401c9d2fa$863a6280$0301a8c0@mal769a60aa920> <88d2415e0905120902x24259365o364835d11f09dd01@mail.gmail.com> <00ce01c9d327$0f3bc390$0301a8c0@mal769a60aa920> Date: Thu, 14 May 2009 09:57:41 +0100 Message-ID: <88d2415e0905140157g7fa534efqa79009cd0f188b36@mail.gmail.com> From: lawrence mayhead 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=001e680f15984c84660469db850f X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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-d229.1 ; domain : googlemail.com DKIM : pass X-Mailer: Unknown (No Version) --001e680f15984c84660469db850f Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit No dispute this time. Laurie 2009/5/12 mal hamilton > Lawerence > No one is disputing downward SLOPE reduces the effective height. We are > discussing 500 Khz PORTABLE and the most convenient way to erect a suitable > antenna with minimum effort and you agree at 500 Khz it will not be a > serious disadvantage to have such a slope. > therefore a single mast and some slope is acceptable. You are AGREEING > wiith me so I am confused by your email !!!!!! The topic is 500 Khz > PORTABLE. > G3KEV > > > ----- Original Message ----- > *From:* lawrence mayhead > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Tuesday, May 12, 2009 5:02 PM > *Subject:* Re: LF: Re: Re: 500kHz Portable > > I fully agree with Mike and Andy, any slope downward will reduce the > effective height of the antenna, and hence its radiation resistance. > This may not be too much of a problem on 500kHz where enough RF can be > generated but on 136 not so good and on 73 useless. > I have proved this in practice as well as by simulation. > So there you are Mal. > Laurie G3AQC > > 2009/5/12 Andy Talbot > >> 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 >>> >>> >>> >> > ------------------------------ > > > 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 > > --001e680f15984c84660469db850f Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable No dispute this time.
Laurie

2009/5/12=20= mal hamilton <= g3kevmal@talktalk.net>
Lawerence
No one is disputing downward SLOPE redu= ces the=20 effective height. We are discussing 500 Khz PORTABLE and the most convenient= way=20 to erect a suitable antenna with minimum effort and you agree at 500 Khz it=20= will=20 not be a serious disadvantage to have such a slope.
therefore a single mast and some slope=20= is=20 acceptable. You are AGREEING wiith me so I am confused by your email !!!!!!=20= The=20 topic is 500 Khz PORTABLE.
G3KEV
=A0
----- Original Message -----
From:=20 lawrence mayhead
Sent: Tuesday, May 12, 2009 5:02 PM
Subject: Re: LF: Re: Re: 500kHz=20 Portable

I fully agree with Mike and Andy, any slope downward will=20 reduce the effective height of the antenna, and hence its radiation=20 resistance.
This may not be too much of a problem on 500kHz where enoug= h RF=20 can be generated but on 136 not so good and on 73=A0 useless.
I have=20 proved this in practice as well as by simulation.
So there you are=20 Mal.
Laurie G3AQC

2009/5/12 Andy Talbot <andy.g4jnt@googl= email.com>
A full quarter wave inverted L with sloping end is starting to beco= me a=20 loop with the ground path forming part of the loop conductor, rather tha= n a=20 vertical.=A0=A0 ANY antenna that approaches more than about a tenth of=20 a wavelength cannot be treated as small any more, and must be considered= in=20 its entirety.=A0 Such is obvious even before resorting to=20 modelling.=A0 Mike was referring to electrically short antennas where th= e=20 downward sloping part simply opposes the current flow in the upward=20 path.=A0=A0=A0
=A0
A small amount of slope on a large capacity hat might not be too=20 noticeable in practice, as a lot of extra capacitance at the top could d= o=20 more good than its slope undoes.
=A0
Please stop and actually think, and perhaps before being so rude=20 and=A0treating all why don't own millions of hectares of farmland as= =20 second-class radio-ams, you stop and read the exam question.

Andy =A0G4JNT
wobbleU cubed=20 .g4jnt.kom


2009/5/12 mal hamilton <= g3kevmal@talktalk= .net>

You=20 are certainly NO EXPERT at amateur radio never mind LF/MF and especial= ly=20 antennas.
I have worked the world on LF/MF using Inv L antennas wit= h=20 the far end just above ground , and in normal CW mode.
Some time ag= o it=20 was Comics, elevated lemonade bottles as coil =A0formers, thought an=20 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,=20 100 ft high and performs well but for some this might be difficult,=20 therefore use what you can get on your property and let the far end ti= lt=20 down if necessary.
G3KEV

----- Original Message ----- From:=20 "Mike Dennison" <mike.dennison@ntlworld.com>
To: <rsgb_lf_group@bl= acksheep.org>
Sent: Tuesday, May=20 12, 2009 10:29 AM
Subject: Re: LF: Re: Re: 500kHz Portable

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

This is quite wrong. A= ny=20 slope downwards will reduce the effective
height of a Marconi. Si= nce=20 ERP is a function of the square of the
effective height this is=20 extremely important. An umbrella is far
preferable to an inverted= -L=20 in a single mast situation because a
large amount of capacitance=20= to=20 ground can be achieved without much
reduction of effective=20 height.

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

Mike,=20 G3XDV
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D



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



No=20 virus found in this incoming message.
Checked by AVG - www.avg.com
Version:=20 8.5.325 / Virus Database: 270.12.25/2109 - Release Date: 05/11/09=20 16:14:00





No virus found in this incoming message.
Checked by AVG -=20 www.avg.com
Versi= on: 8.5.325 / Virus Database: 270.12.25/2109 - Release=20 Date: 05/11/09 16:14:00

--001e680f15984c84660469db850f--