Return-Path: Received: from rly-de05.mx.aol.com (rly-de05.mail.aol.com [172.19.170.141]) by air-de01.mail.aol.com (v123.4) with ESMTP id MAILINDE011-4d64a09b1fc8a; Tue, 12 May 2009 13:30:17 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de05.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDE053-4d64a09b1fc8a; Tue, 12 May 2009 13:29:33 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M3vmT-0004ay-Fj for rs_out_1@blacksheep.org; Tue, 12 May 2009 18:28:41 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M3vmS-0004ap-Rl for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 18:28:40 +0100 Received: from ttsmtp-4.cpwnetworks.com ([62.24.128.245] helo=ttsmtp.cpwnetworks.com) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1M3vmP-0002uz-Q6 for rsgb_lf_group@blacksheep.org; Tue, 12 May 2009 18:28:40 +0100 X-Path: TalkTalk-smtp X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AgEFALtOCUpOlLdA/2dsb2JhbACCJC+BfYc+BsFxhAIF Received: from unknown (HELO mal769a60aa920) ([78.148.183.64]) by ttsmtp.cpwnetworks.com with SMTP; 12 May 2009 18:28:26 +0100 Message-ID: <00ce01c9d327$0f3bc390$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> <88d2415e0905120902x24259365o364835d11f09dd01@mail.gmail.com> Date: Tue, 12 May 2009 18:28:26 +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_00CB_01C9D32F.70C96420" 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_00CB_01C9D32F.70C96420 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Lawerence=20 No one is disputing downward SLOPE reduces the effective height. We are disc= ussing 500 Khz PORTABLE and the most convenient way to erect a suitable ante= nna with minimum effort and you agree at 500 Khz it will not be a serious di= sadvantage to have such a slope.=20 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 -----=20 From: lawrence mayhead=20 To: rsgb_lf_group@blacksheep.org=20 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 effec= tive 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 gen= erated 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=20 2009/5/12 Andy Talbot 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 a=20= vertical. ANY antenna that approaches more than about a tenth of a wavelen= gth cannot be treated as small any more, and must be considered in its entir= ety. Such is obvious even before resorting to modelling. Mike was referrin= g to electrically short antennas where the downward sloping part simply oppo= ses the current flow in the upward path. =20 A small amount of slope on a large capacity hat might not be too noticea= ble 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 tre= ating all why don't own millions of hectares of farmland as second-class rad= io-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 espe= cially 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 former= s, 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 perfor= ms 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" 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 ti= ed to a bush or tree, or a stake in the ground via an insulator, as f= ar away as possible from the vert section, the longer the better. Kee= p 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 fro= m 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: 05/1= 1/09 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_00CB_01C9D32F.70C96420 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Lawerence
No one is disputing downward SLOPE reduces=20= 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 is=20 acceptable. You are AGREEING wiith me so I am confused by your email !!!!!!=20= The=20 topic is 500 Khz PORTABLE.
G3KEV
 
----- Original Message -----
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  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@googlemail.com><= /SPAN>
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.   ANY antenna that approaches more than about a tent= h of=20 a wavelength cannot be treated as small any more, and must be considered= in=20 its entirety.  Such is obvious even before resorting to=20 modelling.  Mike was referring to electrically short antennas where= the=20 downward sloping part simply opposes the current flow in the upward=20 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 d= o=20 more 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.

Andy  G4JNT
wobbleU cubed=20 .g4jnt.kom


2009/5/12 mal hamilton <g3kevmal@ta= lktalk.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  formers, thought a= n=20 AR88D was a  diversity 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_l= f_group@blacksheep.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
Version: 8.5.325 / Virus Database: 270.12.25/2109 - Releas= e=20 Date: 05/11/09 16:14:00
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