Return-Path: Received: from mtain-df12.r1000.mx.aol.com (mtain-df12.r1000.mx.aol.com [172.29.64.224]) by air-da06.mail.aol.com (v129.4) with ESMTP id MAILINDA061-85e84c1bea9b185; Fri, 18 Jun 2010 17:52:27 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-df12.r1000.mx.aol.com (Internet Inbound) with ESMTP id 2688F380000C2; Fri, 18 Jun 2010 17:52:25 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OPjTG-0007ir-4W for rs_out_1@blacksheep.org; Fri, 18 Jun 2010 22:51:30 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OPjTF-0007ii-IQ for rsgb_lf_group@blacksheep.org; Fri, 18 Jun 2010 22:51:29 +0100 Received: from out1.ip05ir2.opaltelecom.net ([62.24.128.241]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OPjTD-0002lC-0W for rsgb_lf_group@blacksheep.org; Fri, 18 Jun 2010 22:51:29 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AiAFACKHG0xcHD+q/2dsb2JhbACBQ51SccJthRsE X-IronPort-AV: E=Sophos;i="4.53,441,1272841200"; d="scan'208,217";a="302963255" Received: from unknown (HELO laptopcore2) ([92.28.63.170]) by out1.ip05ir2.opaltelecom.net with ESMTP; 18 Jun 2010 22:51:20 +0100 From: "g3zjo" To: Date: Fri, 18 Jun 2010 22:51:20 +0100 Message-ID: <001101cb0f30$62e6f0a0$0202a8c0@laptopcore2> MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2616 In-Reply-To: Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: RE: LF: AW: RE: Earth electrode loop area - I'm struggling Content-Type: multipart/alternative; boundary="----=_NextPart_000_0012_01CB0F38.C4AB58A0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_40_50, HTML_FONTCOLOR_UNKNOWN,HTML_FONTCOLOR_UNSAFE,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-global-disposition: G x-aol-sid: 3039ac1d40e04c1bea9964da X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0012_01CB0F38.C4AB58A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Roger =20 I did spot you 3 times tonight -28dB, -29dB and -30dB, using my invert= ed L, normal TX antenna. Nothing on the Doublet, the spots are on the database now although they didn=92t get uploaded at the time. =20 Eddie =20 -----Original Message----- From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Roger Lapthor= n Sent: 18 June 2010 22:42 To: rsgb_lf_group@blacksheep.org Subject: Re: LF: AW: RE: Earth electrode loop area - I'm struggling =20 137kHz is a project for later this year Stefan. 73s Roger G3XBM 2010/6/18 Stefan Sch=E4fer Interesting! I wish i would know my ERP during the 9 kHz test where i reached 2km. But the grabber is still not calibrated :-( Roger, when will you try 137 kHz? 73 es gl Stefan/DK7FC ________________________________ Von: owner-rsgb_lf_group@blacksheep.org im Auftrag von Rik Strobbe Gesendet: Fr 18.06.2010 23:10 An: rsgb_lf_group@blacksheep.org Betreff: LF: RE: Earth electrode loop area - I'm struggling 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 "radiate" 55uW to get 50uW ERP. 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 effective 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 ou= t my effective loop area and I cannot get sensible answers. These are th= e 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.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 ------=_NextPart_000_0012_01CB0F38.C4AB58A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi Roger

 <= /font>

I did spot you= 3 times tonight -28dB, -29dB and -30dB, using my inverted L, normal TX antenna. Nothing on th= e Doublet, the spots are on the database now although they didn’t= get uploaded at the time.

 <= /font>

Eddie

 <= /font>

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksh= eep.org] On Behalf Of = Roger Lapthorn
Sent: 18 June 2010 22:4= 2
To: rsgb_lf_group@black= sheep.org
Subject: Re: LF: AW: RE= : Earth electrode loop area - I'm struggling

 

137kHz is a project for later this year Stefan.

73s
Roger G3XBM

2010/6/18 Stefan= Sch=E4fer <schaefer@hst.tu-da= rmstadt.de>

Interesting!
I wish i would know my ERP during the 9 kHz test where i reached 2km.= But the grabber is still not calibrated :-(

Roger, when will you try 137 kHz?

73 es gl

Stefan/DK7FC

________________________________

Von: owner-rsgb_= lf_group@blacksheep.org im Auftrag von Rik Strobbe
Gesendet: Fr 18.06.2010 23:10
An: rsgb_lf_group@blac= ksheep.org
Betreff: LF: RE: Earth electrode loop area - I'm struggling


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 "radiate" 55uW to get 50uW ERP.
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<= br> 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_g= roup@blacksheep.org] namens Roger Lapthorn [roge= rlapthorn@gmail.com]
Verzonden: vrijdag 18 juni 2010 22:29
Aan: rsgb_lf_group@bla= cksheep.org
Onderwerp: LF: Earth electrode loop area - I'm struggling


Please can someone help me with the maths? I've been trying to work ou= t 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<= br> 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 eit= her my calculations are wrong or the figure is correct and the effective loop= area is very very small.

Help!

73s
Roger G3XBM

--
http://g3= xbm-qrp.blogspot.com/
http://www.g3xbm.= co.uk <http://www.g= 3xbm.co.uk/>
http:/= /www.youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088




--
http://g3xbm-qrp.blogspot.c= om/
http://www.g3xbm.co.uk
http://www.youtube.com/u= ser/g3xbm
G3XBM    GQRP 1678      ISWL G11088

------=_NextPart_000_0012_01CB0F38.C4AB58A0--