Return-Path: Received: (qmail 58219 invoked from network); 6 Jan 2004 08:15:34 -0000 Received: from unknown (HELO ptb-mxscan01.plus.net) (212.159.14.235) by ptb-mailstore01.plus.net with SMTP; 6 Jan 2004 08:15:34 -0000 Received: (qmail 79314 invoked from network); 6 Jan 2004 08:15:34 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 X-Priority: 3 X-MSMail-Priority: Normal Received: from ptb-mxcore01.plus.net (212.159.14.215) by ptb-mxscan01.plus.net with SMTP; 6 Jan 2004 08:15:33 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim) id 1AdmNA-000KPj-P5 for dave@picks.force9.co.uk; Tue, 06 Jan 2004 08:15:32 +0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AdmMR-00061d-Nu for rs_out@blacksheep.org; Tue, 06 Jan 2004 08:14:47 +0000 Received: from [134.58.240.45] (helo=thumbler.kulnet.kuleuven.ac.be) by post.thorcom.com with esmtp (Exim 4.14) id 1AdmMQ-00061T-CG for rsgb_lf_group@blacksheep.org; Tue, 06 Jan 2004 08:14:46 +0000 Received: from localhost (localhost [127.0.0.1]) by thumbler.kulnet.kuleuven.ac.be (Postfix) with ESMTP id 2ED5E1383E9 for ; Tue, 6 Jan 2004 09:14:16 +0100 (CET) Received: from lepidus.kulnet.kuleuven.ac.be (lepidus.kulnet.kuleuven.ac.be [134.58.240.72]) by thumbler.kulnet.kuleuven.ac.be (Postfix) with ESMTP id 8011B138428 for ; Tue, 6 Jan 2004 09:14:15 +0100 (CET) X-Fake-Domain: dell-rik.fys.kuleuven.ac.be Received: from dell-rik.fys.kuleuven.ac.be (pc-10-33-165-177.fys.kuleuven.ac.be [10.33.165.177]) by lepidus.kulnet.kuleuven.ac.be (Postfix) with ESMTP id 39E3D380002 for ; Tue, 6 Jan 2004 09:14:15 +0100 (CET) Message-ID: <5.1.0.14.0.20040106090928.03a8c2a0@u0019445.kuleuven.be> X-Sender: u0019445@u0019445.kuleuven.be X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Tue, 06 Jan 2004 09:16:46 +0100 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" In-reply-to: <6.0.1.1.2.20040105172829.027e8860@POP3.freeler.nl> References: <000201c3d2f3$c4fb5f40$61e4fc3e@l8p8y6> <6.0.1.1.2.20031229161651.027e8660@POP3.freeler.nl> <000001c3d009$acf7a620$c7e47f50@Smisan> <6.0.1.1.2.20040103121138.0280f960@POP3.freeler.nl> <000601c3d2c3$2bd34e70$b733f7c2@johnb5a82ea1a4> <6.0.1.1.2.20040104163146.027efbe0@POP3.freeler.nl> <000201c3d2f3$c4fb5f40$61e4fc3e@l8p8y6> MIME-Version: 1.0 X-Virus-Scanned: by KULeuven Antivirus Cluster Subject: Re: LF: Horizontally polarised radiation Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 Content-transfer-encoding: 8bit Hello group,

It is an "idée fixe" that a horizontal wire must radiate a horizontal polarized EM-wave.
A nice example of a mechanical horizontal construction that radiates a vertical polarized signal is the DDRR antenna.
So a large horizontal topload close to ground will in most cases improve the antenna efficiency (reduce the loss resistance ... footprint theory) but the radiated signal will be nevertheless mainly vertical polarized.

73, Rik ON7YD

At 17:47 5/01/2004 +0100, you wrote:

To All from PA0SE,

In an earlier e-mail I wrote:

----- Original Message -----
From: Dick Rollema
To: rsgb_lf_group@blacksheep.org
Sent: Sunday, January 04, 2004 3:50 PM
Subject: Re: LF: Re: "T" versus "L"aerial

Dear John,

Computer simulation takes place over perfect ground and shows appreciable horizontally polarised radiation under high elevation angles for the inverted-L aerial . But even at say 20m height of the horizontal part of the aerial this is only 0.0009 of a wavelength so the aerial is almost on the ground. This means that over real earth such strong currents will be induced in the earth under the aerial that almost all power in the horizontally polarised field will be converted into heat in its resistance.

Mal, G3KEV commented:

Dick
You are saying that my 4 x inv L antennas each at 120 ft vertical and 400 ft horizontal are only burning up the field under the array.
My signal is reported throughout EU and beyond to Russia and the USA as the strongest on the air only surpassed by MM0ALM when he was active. As far as I can remember he was using 2 x inv L antennas at over 140 ft high using two masts.
I have never used a T antenna, my logic is that the more independent wire in the air the better, you have the benefit in my case of 4 top loaded verticals in parallel. All the bottom ends of the verticals are connected to the top of the loading coil of about 0.3 mh. The top of each L is about 10 feet out from the mast and the drop wires taper to the bottom reducing capacitance to ground.
An inv L antenna is really a top loaded vertical.
I hope you understand what I mean.
Calculations and theoretical assumptions are often way of the mark when it comes to small antenna systems like radio amateurs use on LF.
The only solution is the practical approach, common sense gained with experience and put up the best antenna you can then judge the results. As a matter of interest I have never burnt out any insulators, antenna wires, ground radials or any vegetation underneath the antenna array.
If you are working worldwide on normal CW then you have got it right !!!!!!!
73 de Mal/G3KEV

What I said was that the radiation from the horizontal part of a top loaded aerial is largely absorbed in the earth under it because the wire is so near to the surface.
To have a closer look I modeled a 40m long dipole for 136kHz, made of 1.5mm copper wire over real ground at a height h. Ground constants are dielectric constant 13; conductivity 5mS/m.

The simulation shows that the maximum of radiation is under an elevation of 90 degrees. The gain is referenced to a half wave dipole in free space.

h in metres    gain in dBd

500                   -2.29
200                   -6.65
100                 -11.84
50                  -17.44
20                  -25.40
10                  -31.48

The numbers speak for themselves.

The radiation by the vertical part of the aerial, that does the work, is not affected by this of course.

73, Dick, PA0SE