Return-Path: Received: from mtain-mh07.r1000.mx.aol.com (mtain-mh07.r1000.mx.aol.com [172.29.96.219]) by air-db04.mail.aol.com (v127_r1.1) with ESMTP id MAILINDB044-86984badfbf726e; Sat, 27 Mar 2010 08:37:11 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mh07.r1000.mx.aol.com (Internet Inbound) with ESMTP id AD18738000117; Sat, 27 Mar 2010 08:37:09 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NvVFK-0001ni-1V for rs_out_1@blacksheep.org; Sat, 27 Mar 2010 12:36:10 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NvVFJ-0001nZ-JH for rsgb_lf_group@blacksheep.org; Sat, 27 Mar 2010 12:36:09 +0000 Received: from lnx503.hrz.tu-darmstadt.de ([130.83.156.232]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NvVFG-0004sc-Rd for rsgb_lf_group@blacksheep.org; Sat, 27 Mar 2010 12:36:09 +0000 Received: from FILE-SERVER-HST.hst.e-technik.tu-darmstadt.de (File-Server-HST.hst.e-technik.tu-darmstadt.de [130.83.212.129]) by lnx503.hrz.tu-darmstadt.de (8.14.2/8.14.2/HRZ/PMX) with SMTP id o2RCa6En008580 for ; Sat, 27 Mar 2010 13:36:06 +0100 (envelope-from schaefer@hst.tu-darmstadt.de) Received: from [127.0.0.1] (helo=File-Server-HST.hst.e-technik.tu-darmstadt.de) by FILE-SERVER-HST.hst.e-technik.tu-darmstadt.de with AVK MailGateway; for ; Sat, 27 Mar 2010 13:36:05 +0100 Content-class: urn:content-classes:message MIME-Version: 1.0 X-MimeOLE: Produced By Microsoft Exchange V6.5 Date: Sat, 27 Mar 2010 13:31:36 +0100 Message-ID: <38A51B74B884D74083D7950AD0DD85E82A1BA4@File-Server-HST.hst.e-technik.tu-darmstadt.de> X-MS-Has-Attach: X-MS-TNEF-Correlator: <38A51B74B884D74083D7950AD0DD85E82A1BA4@File-Server-HST.hst.e-technik.tu-darmstadt.de> Thread-Topic: LF: Question about ground impedance at 8.97 KHZ Stefan. Thread-Index: AcrNppcEw3qAX6hzQkGTgtMRGH1gSgAAtpN3 References: <4BAD19D0.300@telia.com> <56DF8C4BED71466A80EB2EB1D99F6788@JimPC> From: =?iso-8859-1?Q?Stefan_Sch=E4fer?= To: X-AVK-Virus-Check: AVB 19.844;26.03.2010 X-PMX-TU: seen v0.99a by 5.5.9.388399, Antispam-Engine: 2.7.2.376379, Antispam-Data: 2010.3.27.122423 X-PMX-SPAMCHECK: outgoing mail X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Content-Type: multipart/mixed; boundary="----_=_NextPart_001_01CACDAA.1179BDA9" Subject: AW: LF: Question about ground impedance at 8.97 KHZ Stefan. X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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-VSS-INFO: 5400.1158/56768 X-AOL-VSS-CODE: clean x-aol-sid: 3039ac1d60db4badfbf56660 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) ------_=_NextPart_001_01CACDAA.1179BDA9 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Addition: When i replace the wire by a fixed capacitor of 570pF (470+100)= i come to resonance at about the same frequency. So my antenna acts as a= 580pF C on <9 just like on 137kHz. =20 If you have a inv-L, the C' (in pF/m) should be even higher? =20 73, Stefan/DK7FC ________________________________ Von: owner-rsgb_lf_group@blacksheep.org im Auftrag von James Moritz Gesendet: Sa 27.03.2010 13:06 An: rsgb_lf_group@blacksheep.org Betreff: Re: LF: Question about ground impedance at 8.97 KHZ Stefan. Dear Paul, LF Group, For Stefan's benefit, 1' =3D 0.3048m, so we are talking about a 52m long= wire. I measured my home QTH inv-L antenna (about 55m of wire in total, about 10= m height) at 10kHz to have a capacitance of about 340pF, in series with a resistance of about 300ohms. This is in a location with several small tree= s, etc., so you could possibly expect lower resistance in an open location,= or higher if you are in a forest! As has been pointed out, it depends on the type of bridge whether you are measuring a series or parallel RC equivalent - for the above antenna, the parallel equivalent would be about 340pF/7.3Megohms. The magnitude of the impedance at 9kHz would be about 52kohms These are much higher impedances than are commonly measured using amateur= RF bridges. If you look at old textbooks on AC bridge measurements, you will see elaborate shielding/guarding measures are often required for high impedance measurements. The basic problem is you are trying to measure a small resistance component while balancing out a much larger, quadrature, capacitive component. So anything that affects the balance of the bridge (e.g. stray coupling between the components, or source or detector), can cause large errors. I imagine good electrostatic shielding between the bridge components and antenna wire would be essential. A first step would= be to check the bridge works accurately on some known impedances (e.g. a low-loss capacitor of a few 100pF with a series resistor). The way I did my measurements was to resonate the antenna at the measureme= nt frequency with a series inductor, then measure the relatively low resistiv= e impedance of the combination with a simple resistance bridge. The loss resistance of the coil was measured by replacing the antenna with a calibrated air-variable capacitor, measuring the resistance again, and subtracting it from the antenna+coil resistance. This still has some potential errors (e.g. due to the stray capacitance of the inductor to ground) but avoids the need to resolve the R/C components, and reflects th= e way the antenna will actually be used. Cheers, Jim Moritz 73 de M0BMU ------_=_NextPart_001_01CACDAA.1179BDA9 Content-Type: application/ms-tnef; name="winmail.dat" Content-Transfer-Encoding: base64 eJ8+IgYMAQaQCAAEAAAAAAABAAEAAQeQBgAIAAAA5AQAAAAAAADoAAEIgAcAGAAAAElQTS5NaWNy b3NvZnQgTWFpbC5Ob3RlADEIAQ2ABAACAAAAAgACAAEEgAEAPQAAAEFXOiBMRjogUXVlc3Rpb24g YWJvdXQgZ3JvdW5kIGltcGVkYW5jZSBhdCA4Ljk3IEtIWiAgU3RlZmFuLgCtEwEFgAMADgAAANoH AwAbAA0AHwAkAAYAVQEBIIADAA4AAADaBwMAGwANACQABQAGADsBAQmAAQAhAAAAMzQ4MDBGN0Mw MkExM0Y0QTgxQ0Y0NkVENEU3RDNEMjUAOAcBA5AGACQUAAA4AAAAAwA2AAAAAABAADkAMUhTcanN ygEeAD0AAQAAAAUAAABBVzogAAAAAAIBRwABAAAAMgAAAGM9REU7YT0gO3A9SFNUO2w9RklMRS1T RVJWRVItSC0xMDAzMjcxMjM2MDVaLTIyMzYAAAAeAEkAAQAAAD0AAABSZTogTEY6IFF1ZXN0aW9u IGFib3V0IGdyb3VuZCBpbXBlZGFuY2UgYXQgOC45NyBLSFogIFN0ZWZhbi4AAAAAQABOAIAja+2l zcoBHgBaAAEAAAAjAAAAb3duZXItcnNnYl9sZl9ncm91cEBibGFja3NoZWVwLm9yZwAAAgFbAAEA AABjAAAAAAAAAIErH6S+oxAZnW4A3QEPVAIAAAAAb3duZXItcnNnYl9sZl9ncm91cEBibGFja3No ZWVwLm9yZwBTTVRQAG93bmVyLXJzZ2JfbGZfZ3JvdXBAYmxhY2tzaGVlcC5vcmcAAAIBXAABAAAA KAAAAFNNVFA6T1dORVItUlNHQl9MRl9HUk9VUEBCTEFDS1NIRUVQLk9SRwAeAF0AAQAAAA0AAABK YW1lcyBNb3JpdHoAAAAAAgFeAAEAAABHAAAAAAAAAIErH6S+oxAZnW4A3QEPVAIAAAAASmFtZXMg TW9yaXR6AFNNVFAAamFtZXMubW9yaXR6QGJ0b3BlbndvcmxkLmNvbQAAAgFfAAEAAAAiAAAAU01U UDpKQU1FUy5NT1JJVFpAQlRPUEVOV09STEQuQ09NAAAAHgBmAAEAAAAFAAAAU01UUAAAAAAeAGcA AQAAACMAAABvd25lci1yc2diX2xmX2dyb3VwQGJsYWNrc2hlZXAub3JnAAAeAGgAAQAAAAUAAABT TVRQAAAAAB4AaQABAAAAHQAAAGphbWVzLm1vcml0ekBidG9wZW53b3JsZC5jb20AAAAAHgBwAAEA AAA5AAAATEY6IFF1ZXN0aW9uIGFib3V0IGdyb3VuZCBpbXBlZGFuY2UgYXQgOC45NyBLSFogIFN0 ZWZhbi4AAAAAAgFxAAEAAAAbAAAAAcrNppcEw3qAX6hzQkGTgtMRGH1gSgAAtpN3AB4AdAABAAAA HQAAAHJzZ2JfbGZfZ3JvdXBAYmxhY2tzaGVlcC5vcmcAAAAAHgAaDAEAAAAPAAAAU3RlZmFuIFNj aORmZXIAAB4AHQ4BAAAAOQAAAExGOiBRdWVzdGlvbiBhYm91dCBncm91bmQgaW1wZWRhbmNlIGF0 IDguOTcgS0haICBTdGVmYW4uAAAAAAIBCRABAAAA0AsAAMwLAAAyIgAATFpGdYKl7sIDAAoAcmNw ZzEyNYIyA0NodG1sMQMwPwEDAfcKgAKkA+MCAGNowQrAc2V0MCAHEwKA/xADAFAEVghVB7IR1Q5R AwHdENcyBgAGwxHVMwRGENlZEu9mNAPGEYo1A8ZUfGFoA3ECgBHjCO8J9zt7G38OMDUcnxxxEeEM YGNnAFALCQFkMzYRYAulNHIgEAIqXA6yAZAOEDkAIDxIVE1MIGSIaXI9IhByPn0h0+cAIQMwIyFk bwDgIyEKsfxccRtgIyEQ8AMwI4URYI0hizMhYCKARUFEI1AJIYw3NyJwVElUTA5FJ30hUA7wUmU6 IBRMRipQUQpQc3RpfQIgIAGgCGAFQAnACGBuNGQgB3BwCYAAcGNlIyswBUA4LjkogEtIWloGAHQB EABwLieNOLo1InAvKL8iIgrjIC+PCzCfDhA2DvA8TUVUEEEgbmEHgD1HRQBORVJBVE9SIMcFoAIw CfB0PSIF4CKTESzgMDAuIMAwMS7zLsAOMDkiJ30qAS8AJz8XKdExzyIhNRFgPEJPHERZJ30g0Tk/ Zzk2MSJwRElWItYsAGQ9MT4QT1dBKjALUHlUiGV4dDMQNjg0I1n/AAAkhSUjJOElfztfPG89d88/ f0CPQZMhqTY0RQpBXwkiBDQ4InBGT05UszSBGxE9IzWwS2IgAJDeejPQFPAtoCyAPQcTRPt+YxPw A7IB0AMxIWBI6EHOZESAKvIqUFdoCfAsAK4gHgALUSyBdE/gIAPwMR4AIGJ5KzBMMGl4awmANIBh CrBjT2AFsW8BI+A1NzBwRiAo0jRS4CsxNbApUBEFoOsHgFCwb1AxcwIgLGYrRN1QwnMzsUwwHgBx ClAscOx5LgYAVFBtUWE0sjOgaSswY3QEIGFX8VLAOD1S8kNSkAOgIYs/UCAmNyIQAoAjdzxI6CJg anVhKuAgbGlrLJArETFAMzdrSHouIYw1/T0hL0qiI1kjZ0dLAcAjZ68Kol8oCoAhjDAnAS89Uf9e f0k/Qq9Dv0TPRd9fX0f//2R/ShxL32gLTg9sfl3vZB8hWUxuYnNwWklcJ/5hAUBp72BfYW9if2OP c4//Za9mv2fPaN92P2r/e19tH1duL28/TmtJI+B5CGAgDREAdiyRLABudi1MsixQs0MnUyALgCBT AJQvbVOwcxpAdWwr8BpiLJBliJADoGhpZ/lP4HI/cR9yL18vdy94P/95T3pfgw98f32Pfp9/r4C/ /4HPgt+D74T/hg9wL4vvjP//n090b3V/jl+Pb5B/kY+hj/+Tr5S/lc+W35fvmP+aD6pvz5wvnT+e T7HGNzOJMC104akASzdGQ5/foO+N7/+l76b/qA+pH7HPvY++n6qf36uvrL+tz67fwj8xDiA6cX5S I1oKsQqBx2/C/8QLSBs0cAGRSSvgPvA9LTHLtMwAUHEA4HFqDGCKoOJiAzB+IF/QAs/BJAD9C4Bl u/PKL8s+sC+xP7JP/bNfPRoktM8DMS7g1L9Zh+86gMWLz7HZV1ZPkcw8yOEuL9r6uelSkHfQsHIt gREgZ2JfbGZfK6JscEACYADQa4pgCeBwWi4FsGcsARFwdQGAcmkiMCB2KxFKM7EEIE37BbBPYHrH /T0hyRzQktEvd9o/20/mEkcHkAnwAQB0j9zP3d/e5wYQIDI3NaAcMy4B0FOAXIE6MDb/41/kb+V/ 5o/nn07V3L/qj//e2N/f4Ontb+5/74/wn/Gv/fpEQhFAHgABIPM/9E/e5/8qPytPLF8tZvev+L/5 z7f//7kPBq8EvwXPuk+7X7xvwD//CM/Rz8vfxHfFixGPEp/TWf0icFDJPxVoFM8Jz9Y91+/J2TlE ZRcRUGGKkIkw9wCw6PD2ciwJ/wsPBk8gb9shfyKJRlJxLXQnWCCK0CvQsFGgdIkwMYmgPSDlNcAz EDA4bYkwVJBQ8OcC0VEhzXBsayJA4YABhP1YQTLhsEsQKWFRAgQfJD9vIk8rHywvLTpJVwAfAHM+ df2AAjBXEdehAtBRVJZIiNRXNygBhDU14bD/UqFRA4nRUmApEYkwAYRTgL5tLf8vDy0cT+CLYXRT sP8C8VOAXMFUMoh1UgUCo1Kh+QGEMzRS8YkwidHpIOMQ/+LBUQBQwAFwNa82vy0cVHEOaVvgOs1L kG9obXP9VsBUi1BYIEICAWEqQVIAvwEzPLPpIIiQ4hDHMHPXwP5sxzD9ceLAIC8+Hy0N6WA8Yy4o U4gyU/CKknBv/nOzsPbAUWDN0AJwV9AqQd8ooFKAQBlCYgFgbwJwAWD/QraJMFJwRN9F7zfNi2MC QLeIFCjSQmNmUnABESFMj99Nny0fUZ9Sr1O5QSbgiHD/JuKLIUkAU3ADwIqwAaE78XcDAOlQS4Fk JuBcYYlSdJZ5AnBAsmLjEGRnAtD+d4uAiVFKQFAlVG9Vf1OMvzEUKVM8NiZBFwFEMWXHMIRSQ4rw cXVpdrSg+4sgAwAtUOKJQwGBiJIy1L+JM1v/XQ9TjGBXYRl3ioaFO0kv7HAzTWVnQYbTAtDXwGdu 4yB16VBAsu9jX2RvZX8CWzk5cmfNKhD+a0GCax9sL1OPcM9x33Lp52nR6SBQU211xvBPdwJmnybg iVBLQSjSSKBtbeJg+0lhMRd1s7ApYtfAA8AxUP0AYEZzn3SvcrxalEGxiAVpSgBvawLib4qhA8B4 7nQBkH9wWYNBYPBalTEV/zEQMtBEsIgjNCBEQHtffG//crzpIIrh4MABkOIQA8CKUcc8cIqgKVEv Z3UXEIcS/zEGJuAo0kDAMuFKUWEhMWL/YeKLUoLvg/9tPwKFgYpptPJiMTBpY2BAAfD2wIHg90Ii UCbFYHkpUjmxMRU8//+LL4TvRCNAGXkxSQDQsGeS/0HwYKCO4eDAArApUim0dzOf4MDhcN+ggkBh IGFkhnH/MVFEz5K/cq06VWFAlalBwPZTOcC3QHliIJCzOeAp0f/9oEnBeIKWpmqWWoWZT5pf9XK8 KCrQZ0HAUTDiEElw3UihcHKR4YBX0HQooEuR/2IilceCMSZBKHAxUDriSkC36VFJwVEAKYJAQtBu oM+/od+bbnpQAtCYE0mAcgHwB/XgKuz7cSZuYnNw4jupmSdhMN7JMPDhoP8YAHKhAdB/YImQYLBJ wQHw/0BRATCPMIbHpQqoT6lffX//WsKl2DKxiZAyxjQjZ8fiwO/pIQEwn4BBwEHXIMUgUTD/pBH3 QGe3so+zn3K8ObHG8G9JwH+AoChnsXKAgddAYz8xUHrRSWHiYShwMfFrbn/fcXfqo8SRr7tPcq1K AS0/SgBJIDpGJkFAwtcgZXf/NWE7wTylPDZAFKfBKu/Cn/9yr8hfyW913TQQpFEw8IcQ/zGDgYrO YXiBOcBREeJghoL/YiMy1QLxYiKBics/zE/KXHZmiSJLkGNJcMa8ykBk/3dAp7FjMwFgkSZiIv2A hjD/nKJJYUoBSlWcsdL/1A+MX/cChZ/1eTFiykBC6V+RAlH/lpFAGVqUabTE0tqv278/P99ASaWU grDQAzEXYklw/YD/pLA6gZ4z0Tg8v+K/48+cE9/KMFqQetG2wTQwLWFQoHD/hkCWkcUngkBe+Njk QDcYAD/s4EwxtqHpP+pPhQ11Yn+kMUnQX1JY8dXwMeDRCiv/5iNAGEHFASFEQVeSv8Lwn//xr2Wt NLC4dKv1o7XXkCjx/znAYiKkJTpsYiLXdjmh99+7+O/KXGcf4VlgOQBiKcJ+dlgwWXFiIicgMXHQ VWzzYpFiIlIvgPCl2rai2SD+ZrBinxP/PwBPylzOcugcf0RB8+GHcERASXBoIathZL/ILwfvyk8M bw1/DopDBsDLQ8CCMUqvgCBNUQAnUM56D08QXw5sNzNZERLw8DBCTVUTbxR/Dm8XT/8YXxlvGn8b jxyfHa8evx/PBSDQNSEBL0ZPTlTvIVmt1x/wreZcYFElOCJYTyHwYFEiX6zGNzIkEVAbIVAgHDCt UCQgRElWIySPKK9nNTgkEUJPJERZKi0yNyQRSFQUTUwhUH0wEB4ANRABAAAAVwAAADwzOEE1MUI3 NEI4ODRENzQwODNENzk1MEFEMEREODVFODJBMUJBNEBGaWxlLVNlcnZlci1IU1QuaHN0LmUtdGVj aG5pay50dS1kYXJtc3RhZHQuZGU+AAAeADkQAQAAAHAAAAA8TUZFSklLQ0xDTVBERkhPS01BTkFN RU1FT0VBQS5wYXVsY0BzbmV0Lm5ldD4gPDRCQUQxOUQwLjMwMEB0ZWxpYS5jb20+IDw1NkRGOEM0 QkVENzE0NjZBODBFQjJFQjFEOTlGNjc4OEBKaW1QQz4AHgBHEAEAAAAPAAAAbWVzc2FnZS9yZmM4 MjIAAAsA8hABAAAAHwDzEAEAAACKAAAAQQBXACUAMwBBACAATABGACUAMwBBACAAUQB1AGUAcwB0 AGkAbwBuACAAYQBiAG8AdQB0ACAAZwByAG8AdQBuAGQAIABpAG0AcABlAGQAYQBuAGMAZQAgAGEA dAAgADgALgA5ADcAIABLAEgAWgAgACAAUwB0AGUAZgBhAG4ALgAuAEUATQBMAAAAAAALAPYQAAAA AEAABzDX5VBxqc3KAUAACDBrqYURqs3KAQMA3j+vbwAAAwDxPwcEAAAeAPg/AQAAAA8AAABTdGVm YW4gU2No5GZlcgAAAgH5PwEAAABcAAAAAAAAANynQMjAQhAatLkIACsv4YIBAAAAAAAAAC9PPUhT VC9PVT1FUlNURSBBRE1JTklTVFJBVElWRSBHUlVQUEUvQ049UkVDSVBJRU5UUy9DTj1TQ0hBRUZF UgAeAPo/AQAAABUAAABTeXN0ZW0gQWRtaW5pc3RyYXRvcgAAAAACAfs/AQAAAB4AAAAAAAAA3KdA yMBCEBq0uQgAKy/hggEAAAAAAAAALgAAAAMA/T/kBAAAAwAZQAAAAAADABpAAAAAAAMAHUAAAAAA AwAeQAAAAAAeADBAAQAAAAkAAABTQ0hBRUZFUgAAAAAeADFAAQAAAAkAAABTQ0hBRUZFUgAAAAAe ADJAAQAAACMAAABvd25lci1yc2diX2xmX2dyb3VwQGJsYWNrc2hlZXAub3JnAAAeADNAAQAAAB0A AABqYW1lcy5tb3JpdHpAYnRvcGVud29ybGQuY29tAAAAAB4AOEABAAAACQAAAFNDSEFFRkVSAAAA AB4AOUABAAAAAgAAAC4AAAADAHZA/////wsAKQAAAAAACwAjAAAAAAADAAYQOg1xwgMABxBQCAAA AwAQEAAAAAADABEQAAAAAB4ACBABAAAAZQAAAEFERElUSU9OOldIRU5JUkVQTEFDRVRIRVdJUkVC WUFGSVhFRENBUEFDSVRPUk9GNTcwUEYoNDcwKzEwMClJQ09NRVRPUkVTT05BTkNFQVRBQk9VVFRI RVNBTUVGUkVRVUVOQ1kAAAAAAgF/AAEAAABXAAAAPDM4QTUxQjc0Qjg4NEQ3NDA4M0Q3OTUwQUQw REQ4NUU4MkExQkE0QEZpbGUtU2VydmVyLUhTVC5oc3QuZS10ZWNobmlrLnR1LWRhcm1zdGFkdC5k ZT4AAOPg ------_=_NextPart_001_01CACDAA.1179BDA9--