Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mk06.r1000.mx.aol.com (Internet Inbound) with ESMTP id BF04B38000090; Thu, 2 Aug 2012 17:13:27 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Sx2ga-00021T-NF for rs_out_1@blacksheep.org; Thu, 02 Aug 2012 22:12:00 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Sx2gZ-00021K-S8 for rsgb_lf_group@blacksheep.org; Thu, 02 Aug 2012 22:11:59 +0100 Received: from imr-mb02.mx.aol.com ([64.12.207.163]) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1Sx2gX-0007KH-8v for rsgb_lf_group@blacksheep.org; Thu, 02 Aug 2012 22:11:58 +0100 Received: from mtaout-mb04.r1000.mx.aol.com (mtaout-mb04.r1000.mx.aol.com [172.29.41.68]) by imr-mb02.mx.aol.com (8.14.1/8.14.1) with ESMTP id q72LBjdR006585 for ; Thu, 2 Aug 2012 17:11:45 -0400 Received: from White (nrbg-4d072b97.pool.mediaWays.net [77.7.43.151]) by mtaout-mb04.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 35E7AE0000F8 for ; Thu, 2 Aug 2012 17:11:42 -0400 (EDT) Message-ID: <48F83C9119F14E9FA00D50447274460B@White> From: "Markus Vester" To: References: <67c4e86218e0fe1d934327099833d80e@email.freenet.de> <5015CB44.4060800@iup.uni-heidelberg.de> <501728EF.60401@iup.uni-heidelberg.de> <501AA1EF.1070506@iup.uni-heidelberg.de> Date: Thu, 2 Aug 2012 23:11:43 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20110426; t=1343941905; bh=MCXFRtR9jIBlTxonlX/MO8/H1pPMSaumfRBa+u7KIyo=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=NDuEABftMev/PrdSP6C2wXWPXjiWQHXWA9GhWZLI/w1AtJ2ZcYuOfOjJiJh9IxCkx iF2u0OAPxP8yf8kqimhu0YvzzS9LY4Nw6ZVckQNwDQljU2434SSkmvCohBPFhrwF42 T3GvDy7oWACt1QYSDK/dofqPJYntXFdiBQO35h+8= X-AOL-SCOLL-SCORE: 0:2:474108512:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Thank you Stefan for this interesting experiment and report. Here are a couple of thoughts I have discussed with Stefan, and which I would like to share with the group. Regarding the decrease of the resonance frequency close to earth: The wire is a line with distributed capacitance and inductance. If you would bring a halfwave line in close proximity to a perfectly conducting plane, the capacitance would be increased. But at the same time the inductance would decrease, as the magnetic flux would be confined by the smaller gap between the wire and the ground plane. So the wave impedance would go down but the resonance frequency would remain nearly unchanged. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [64.12.207.163 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 4a8faa6952847c1ec651f883b63fc053 Subject: Re: LF: MF: 630m band dipole tests today Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CD7104.2E992A10" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_NAME 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-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:495258432:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m415.1 ; domain : mx.aol.com DKIM : pass x-aol-sid: 3039ac1d618a501aed772a68 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Dies ist eine mehrteilige Nachricht im MIME-Format. ------=_NextPart_000_0009_01CD7104.2E992A10 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Thank you Stefan for this interesting experiment and report. Here are a = couple of thoughts I have discussed with Stefan, and which I would like = to share with the group. Regarding the decrease of the resonance frequency close to earth: The = wire is a line with distributed capacitance and inductance. If you would = bring a halfwave line in close proximity to a perfectly conducting = plane, the capacitance would be increased. But at the same time the = inductance would decrease, as the magnetic flux would be confined by the = smaller gap between the wire and the ground plane. So the wave impedance = would go down but the resonance frequency would remain nearly unchanged. = A couple of meters above real ground, the capacitance would still be = increased as long as its impedance is high compared to that of the soil. = However the magnetic fields will penetrate the soil to some depth, so = the effect on the inductance is much less. Thus the resonant frequency = will go down at low height. However when the wire is actually laid on the ground, the capacitance = becomes so large that its impedance falls below the ohmic ground = resistance. So then you will end up with a nonresonant nearly real = impedance - just what Stefan observed. Regarding the radiation pattern: An low dipole, oriented eg. in the E-W = direction, would be expected to have three distinct modes of radiation: - a high angle skywave ("Near Vertical Incidence Skywave"), with more or = less omnidirectional pattern, and the E-field vector polarized E-W, - a horizontally polarized low angle radiation, broadside to N and S. = However this would be heavily attenuated by the ground acting as a short = circuit, and would not be able to develop into a propagating ground = wave, =20 - a vertically polarized groundwave to the E and W, generated by an = earth loop formed by the wire and the subsurface return current. This is = the same mechanism as in the VLF earth-antenna experiments, only with = the galvanic end contacts replaced by capacitive coupling. I believe = that this mode enabled the daytime QSO between Stefan and myself, 180 km = due east of him. This axial radiation would of course not be present for = a free space dipole. Best 73, Markus (DF6NM). From: Stefan Sch=C3=A4fer=20 Sent: Thursday, August 02, 2012 5:51 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: MF: 630m band dipole tests today MF,=20 Here is my report of the MF dipole experiment of last saturday: = https://dl.dropbox.com/u/19882028/MF/A%20full%20size%20dipole%20for%20the= %20630%20m%20band.pdf 73, Stefan/DK7FC ------=_NextPart_000_0009_01CD7104.2E992A10 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Thank you Stefan for this interesting = experiment=20 and report. Here are a couple of = thoughts I have=20 discussed with Stefan, and which I would like to share with the=20 group.
 
Regarding the decrease of the resonance = frequency=20 close to earth: The wire is a line with = distributed capacitance and=20 inductance. If you would bring a halfwave line in close proximity = to a=20 perfectly conducting plane, the capacitance would be increased. But at = the same=20 time the inductance would decrease, as the magnetic flux would be = confined=20 by the smaller gap between the wire and the ground plane. So the = wave=20 impedance would go down but the resonance frequency would = remain=20 nearly unchanged.
 
A couple of meters above real ground, = the=20 capacitance would still be increased as long as its = impedance is=20 high compared to that of the soil. However the magnetic fields=20 will penetrate the soil to some depth, so the effect on the = inductance is=20 much less. Thus the resonant frequency will go down at low = height.
 
However when the wire is actually = laid on the=20 ground, the capacitance becomes so large that its impedance falls below=20 the ohmic ground resistance. So then you will end up with a = nonresonant=20 nearly real impedance - just what Stefan observed.
 
Regarding the radiation = pattern: An low=20 dipole, oriented eg. in the E-W direction, would be expected to have=20 three distinct modes of radiation:
 
- a high angle skywave ("Near = Vertical=20 Incidence Skywave"), with more or less omnidirectional pattern, and the = E-field=20 vector polarized E-W,
 
- a horizontally polarized low angle = radiation,=20 broadside to N and S. However this would be heavily attenuated by the = ground=20 acting as a short circuit, and would not be able to develop into a=20 propagating ground wave,  
 
- a vertically polarized groundwave to = the E and W,=20 generated by an earth loop formed by the wire and the = subsurface=20 return current. This is the same mechanism as in the VLF earth-antenna=20 experiments, only with the galvanic end contacts replaced by capacitive=20 coupling. I believe that this mode enabled the daytime QSO between = Stefan and=20 myself, 180 km due east of him. This axial radiation would of course not = be=20 present for a free space dipole.
 
Best 73,
Markus (DF6NM).

From: Stefan = Sch=C3=A4fer
Sent: Thursday, August 02, 2012 5:51 PM
To: rsgb_lf_group@blacksheep.org= =20
Subject: Re: LF: MF: 630m band dipole tests = today

MF,

Here is my report of the MF dipole experiment of last = saturday:=20 https://dl.dropbox.com/u/19882028/MF/A%20f= ull%20size%20dipole%20for%20the%20630%20m%20band.pdf

73,=20 Stefan/DK7FC
 
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