Return-Path: Received: from rly-db06.mx.aol.com (rly-db06.mail.aol.com [172.19.130.81]) by air-db04.mail.aol.com (v123.4) with ESMTP id MAILINDB044-ad14a097f492ae; Tue, 12 May 2009 09:53:30 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-db06.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDB067-ad14a097f492ae; Tue, 12 May 2009 09:53:15 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M3sPL-0003CJ-Fb for rs_out_1@blacksheep.org; Tue, 12 May 2009 14:52:35 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M3sPK-0003CA-Sf for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 14:52:34 +0100 Received: from ttsmtp-3.cpwnetworks.com ([62.24.128.244] helo=ttsmtp.cpwnetworks.com) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M3sPH-000888-Ki for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 14:52:34 +0100 X-Path: TalkTalk-smtp X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgEFAK4bCUpOlLdA/2dsb2JhbACCJC+BfYc+BsBohAIF Received: from unknown (HELO mal769a60aa920) ([78.148.183.64]) by ttsmtp.cpwnetworks.com with SMTP; 12 May 2009 14:52:25 +0100 Message-ID: <008e01c9d308$e1c987d0$0301a8c0@mal769a60aa920> From: "mal hamilton" To: 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 14:52:25 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Karma: unknown: 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="----=_NextPart_000_008B_01C9D311.4354B760" 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 ------=_NextPart_000_008B_01C9D311.4354B760 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, May 12, 2009 2:16 PM Subject: Re: LF: Re: Re: 500kHz Portable A full quarter wave inverted L with sloping end is starting to become a lo= op with the ground path forming part of the loop conductor, rather than a ve= rtical. ANY antenna that approaches more than about a tenth of a wavelengt= h cannot be treated as small any more, and must be considered in its entiret= y. Such is obvious even before resorting to modelling. Mike was referring=20= to electrically short antennas where the downward sloping part simply oppose= s the current flow in the upward path. =20 A small amount of slope on a large capacity hat might not be too noticeabl= e in practice, as a lot of extra capacitance at the top could do more good t= han its slope undoes. Please stop and actually think, and perhaps before being so rude and treat= ing all why don't own millions of hectares of farmland as second-class radio= -ams, you stop and read the exam question. I QUOTE from emails sent on the reflector by the man himself, but forgot=20= to mention the TOOTHBRUSH INSULATORS. If one is serious about LF/MFantennas and putting out a respectable signal= then perhaps some hectares would be an advantage.=20 Now is the time to buy. G3KEV =20 Andy G4JNT wobbleU cubed .g4jnt.kom 2009/5/12 mal hamilton You are certainly NO EXPERT at amateur radio never mind LF/MF and especi= ally antennas. I have worked the world on LF/MF using Inv L antennas with the far end j= ust 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 o= n your property and let the far end tilt down if necessary. G3KEV ----- Original Message ----- From: "Mike Dennison" 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=20= 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 =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 ----------------------------------------------------------------------------= -- No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.5.325 / Virus Database: 270.12.25/2109 - Release Date: 05/11/09= 16:14:00 ------=_NextPart_000_008B_01C9D311.4354B760 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
Andy Talbot
Sent: Tuesday, May 12, 2009 2:16 PM=
Subject: Re: LF: Re: Re: 500kHz=20 Portable

A full quarter wave inverted L with sloping end is starting to become= a=20 loop with the ground path forming part of the loop conductor, rather than=20= a=20 vertical.   ANY antenna that approaches more than about a tenth=20= of a=20 wavelength cannot be treated as small any more, and must be considered in=20= its=20 entirety.  Such is obvious even before resorting to modelling. =20= Mike=20 was referring to electrically short antennas where the downward sloping pa= rt=20 simply opposes the current flow in the upward path.   
 
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 do=20= more=20 good than its slope undoes.
 
Please stop and actually think, and perhaps before being so rude=20 and treating all why don't own millions of hectares of farmland as=20 second-class radio-ams, you stop and read the exam question.
 
I QUOTE from emails sent on the reflector= by the=20 man himself,  but forgot to mention the TOOTHBRUSH=20 INSULATORS.
If one is serious about LF/MFantennas and= putting=20 out a respectable signal then perhaps some hectares would be an=20 advantage. 
Now is the time to buy.
G3KEV
 
 

Andy  G4JNTwobbleU=20 cubed .g4jnt.kom


2009/5/12 mal hamilton <g3kevmal@talktalk.net><= BR>
You=20 are certainly NO EXPERT at amateur radio never mind LF/MF and especially= =20 antennas.
I have worked the world on LF/MF using Inv L antennas with=20= the=20 far end just above ground , and in normal CW mode.
Some time ago it w= as=20 Comics, elevated lemonade bottles as coil  formers, thought an AR88= D=20 was a  diversity fly catcher.
What is coming next? The diversity= =20 UMBRELLA!!!!
My current MF antenna is a full 1/4 wave inv L, 100 ft h= igh=20 and performs well but for some this might be difficult, therefore use wh= at=20 you can get on your property and let the far end tilt down if=20 necessary.
G3KEV

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


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 bush=20= 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. Any= slope=20 downwards will reduce the effective
height of a Marconi. Since ERP=20= is a=20 function of the square of the
effective height this is extremely=20 important. An umbrella is far
preferable to an inverted-L in a sing= le=20 mast situation because a
large amount of capacitance to ground can=20= be=20 achieved without much
reduction of effective height.

Based o= n my=20 experience of LF portable (both on 73 and 136kHz), my
advice is to=20= make=20 very sure that the remote ends of a Marconi are
very well insulated= as=20 they carry large voltages. Keep well away from
wet trees. This is n= ot=20 just a safety issue; any 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: 8.5.325= =20 / 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
Version: 8.5.325 / Virus Database: 270.12.25/2109 - Releas= e=20 Date: 05/11/09 16:14:00
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