Return-Path: Received: from mtain-dd09.r1000.mx.aol.com (mtain-dd09.r1000.mx.aol.com [172.29.64.149]) by air-dc01.mail.aol.com (v129.4) with ESMTP id MAILINDC012-86254c1be130ca; Fri, 18 Jun 2010 17:12:16 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dd09.r1000.mx.aol.com (Internet Inbound) with ESMTP id A7FEF38000085; Fri, 18 Jun 2010 17:12:13 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OPiqC-00075S-2C for rs_out_1@blacksheep.org; Fri, 18 Jun 2010 22:11:08 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OPiqB-00075J-Je for rsgb_lf_group@blacksheep.org; Fri, 18 Jun 2010 22:11:07 +0100 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OPiq8-0002PE-Eo for rsgb_lf_group@blacksheep.org; Fri, 18 Jun 2010 22:11:07 +0100 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 707D07B8048 for ; Fri, 18 Jun 2010 23:10:53 +0200 (CEST) Received: from ICTS-S-HUB-N2.luna.kuleuven.be (icts-s-hub-n2.luna.kuleuven.be [10.112.9.12]) by smtps01.kuleuven.be (Postfix) with ESMTP id 44C5C31E702 for ; Fri, 18 Jun 2010 23:10:53 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N2.luna.kuleuven.be ([10.112.9.12]) with mapi; Fri, 18 Jun 2010 23:10:53 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Fri, 18 Jun 2010 23:10:52 +0200 Thread-Topic: Earth electrode loop area - I'm struggling Thread-Index: AcsPJZhs2J6LecK2S8aSj2vO0xVVGgAAeUnX Message-ID: References: In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: RE: Earth electrode loop area - I'm struggling Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C5107CB129BICTSSEXC2CAlu_" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,HTML_MESSAGE, TO_ADDRESS_EQ_REAL 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-sid: 3039ac1d40954c1be12d4e3d X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C5107CB129BICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Roger, my pennyworth: assuming - 50uW ERP - antenna is traded as a loop (gain =3D -0.4dBd) Due to the negative gain (-0.4dB versus dipole) a loop antenna must "radia= te" 55uW to get 50uW ERP. Since the antenna feeding current is 0.15A the radiation resistance is 2.4= 4 milliOhm (R=3D P/I^2) The radiation resistance of a small loop is : Ra =3D 320xPi^4*A^2/L^4 where A =3D loop area (m^2) and L =3D wavelength (m) For 500kHz Ra =3D 5*10^(-7)*A^2 or A =3D 1416*sqrt(Ra) If Ra =3D 0.00244 Ohm then effective the loop area is 70m^2 73, Rik ON7YD - OR7T ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Roger Lapthorn [rogerlapthorn@gmail.com] Verzonden: vrijdag 18 juni 2010 22:29 Aan: rsgb_lf_group@blacksheep.org Onderwerp: LF: Earth electrode loop area - I'm struggling Please can someone help me with the maths? I've been trying to work out my= effective loop area and I cannot get sensible answers. These are the meas= ured or estimated numbers I have: Voltage across "loop" =3D 24.48V rms - measured Current flowing in "loop" =3D 0.15A - measured ERP (from far field levels) =3D 50-100uW (may be less) based on -18dB S/N= with M0BMU >From these figures I should be able to work out the loop area, but either= my calculations are wrong or the figure is correct and the effective loop= area is very very small. Help! 73s Roger G3XBM -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --_000_BF4A524700075746A6467658DFC7102C5107CB129BICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Roger,
 
my pennyworth:
 
assuming
- 50uW= ERP
- antenna is traded as a loop (gain= =3D -0.4dBd)
 
Due to the negative gain (-0.4dB ver= sus dipole) a loop antenna must "radiate" 55uW to get 50uW ERP.<= /font>
Since the antenna feeding current is= 0.15A the radiation resistance is 2.44 milliOhm (R=3D P/I^2)
The radiation resistance of a small= loop is : Ra =3D 320xPi^4*A^2/L^4
where A =3D loop area (m^2) and = ;L =3D wavelength (m)
For 500kHz Ra =3D 5*10^(-7)*A^2 or= A =3D 1416*sqrt(Ra)
If Ra =3D 0.00244 Ohm then effe= ctive the loop area is 70m^2
 
73, Rik  ON7YD - OR7T
 
 
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger= Lapthorn [rogerlapthorn@gmail.com]
Verzonden: vrijdag 18 juni 2010 22:29
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: Earth electrode loop area - I'm struggling

Please can someone help me with the maths? I've been trying to work= out my effective loop area and I cannot get sensible answers. These are= the measured or estimated numbers I have:

Voltage across "loop"  =3D 24.48V rms  - measured
Current flowing in "loop" =3D 0.15A - measured
ERP (from far field levels) =3D 50-100uW (may be less) based on -18dB S/N= with M0BMU

>From these figures I should be able to work out the loop area, but either= my calculations are wrong or the figure is correct and the effective loop= area is very very small.

Help!

73s
Roger G3XBM

--
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.u= k
http://www= .youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088
--_000_BF4A524700075746A6467658DFC7102C5107CB129BICTSSEXC2CAlu_--