Return-Path: Received: from mtain-de07.r1000.mx.aol.com (mtain-de07.r1000.mx.aol.com [172.29.64.207]) by air-dc10.mail.aol.com (v129.4) with ESMTP id MAILINDC104-86a84c62b2812d2; Wed, 11 Aug 2010 10:24:01 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-de07.r1000.mx.aol.com (Internet Inbound) with ESMTP id 10291380000C2; Wed, 11 Aug 2010 10:23:52 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OjCCX-0001lk-Sa for rs_out_1@blacksheep.org; Wed, 11 Aug 2010 15:22:41 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OjCCX-0001lb-DR for rsgb_lf_group@blacksheep.org; Wed, 11 Aug 2010 15:22:41 +0100 Received: from mail-bw0-f43.google.com ([209.85.214.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OjCCV-0002WV-14 for rsgb_lf_group@blacksheep.org; Wed, 11 Aug 2010 15:22:41 +0100 Received: by bwz11 with SMTP id 11so166159bwz.16 for ; Wed, 11 Aug 2010 07:22:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:date:message-id :subject:from:to:content-type; bh=cI5q0R8TBV8Nh4NEUP3OVCxXeOBV5f7x84EBJfxqVSg=; b=bAShy6xPC0O0zkQtmxPWifNqHuCiH3vftm+cGT72BAvz0ULMiVyMTnPoew89RtAtss e2Q+UlyAqVHLClkupzQHrHi37Tl/uQxh6qd3JBeeNyzcIdlhOJXKo6kr9gd38W4c7kwh f/n53qJBFIRPy1puWzbh/dL8YMq3m0TYCnksA= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=O2h3Y+EbJGdc2vUwhnU4XkHnV2va5aewGTbDIstfW8J64VqO7dW4Q+r4OCdoIo3pUF RkCd1dmBLbcrvTZ8jTl7kxFTh3S3QnulDPbLKwAKutuKEJOpGak3EDYnBNWm88nFkWkb S0/8TCvN2XUkPomNREbq6bZWNe1Ygw4l2BowA= MIME-Version: 1.0 Received: by 10.204.59.9 with SMTP id j9mr5278516bkh.150.1281536556563; Wed, 11 Aug 2010 07:22:36 -0700 (PDT) Received: by 10.204.194.69 with HTTP; Wed, 11 Aug 2010 07:22:36 -0700 (PDT) Date: Wed, 11 Aug 2010 15:22:36 +0100 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org, Alan Melia DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: 136kHz ERP calculation (G3XBM's earth electrode antenna) Content-Type: multipart/alternative; boundary=001636eefc8a387d17048d8cfbe9 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_40_50,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-sid: 3039ac1d40cf4c62b2781a8d X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --001636eefc8a387d17048d8cfbe9 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Background from Alan Melia..... *=93Hi Roger you can calibrate your loop first using DCF39 on 138.83. This= has a field strength in our area of 1mV/m. Then you could work back your own= ERP by comparison...... 1W ERP produces 300mV/m at 1km, 100mV/m at 10km (from memory ....I think that is correct....10dB per decade after 1km). Doing= it that way removes as lot of the variables, and its a good thumbnail calculation.=94* So, this afternoon I measured the strength of DCF39 as *-22.8dB* using the same loop and receiver and Spectran settings, so -22.8dB is equivalent to 1mV/m field strength based on Alan=92s assumptions. G3XBM=92s signals at 14.9km measured -42.5dB which is approximately *100uV= /m*. Assuming 100mV/m at 10km equals 1W ERP, then *64mV/m* would equal 1W ERP= at 14.9kms (approximately 4dB weaker signal from the CCIR curves). The ERP is lower by the ratio of 100uV/m to 64mV/m. So, my ERP in the best direction= is 56dB down on 1W, which is *2.5uW ERP*. If this calculation is correct then I=92m surprised that such a low power= (2W from PA) into such a strange antenna structure (20m separated ground rods connected by wire just 1.5m above ground for most of the run) can produce= so *much* ERP. Please can you check these figures Alan (or others) and see if you agree? 73s Roger G3XBM --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --001636eefc8a387d17048d8cfbe9 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable <= meta name=3D"ProgId" content=3D"Word.Document">

= Background from Alan Melia.....

= =A0

=93Hi Roger you can calibrate= your loop first using DCF39 on 138.83. This has a field strength in our area of 1mV/= m. Then you could work back your own ERP by comparison...... 1W ERP produc= es 300mV/m at 1km, 100mV/m at 10km (from memory ....I think that is correc= t....10dB per decade after 1km). =A0Doing it that way removes as lot of the variables, and its a good thumbnail calc= ulation.=94

= =A0

= So, this afternoon I measured the st= rength of DCF39 as -22.8dB using the same loop and receiver and Spectran settings, so -22.8dB is equivalent to= 1mV/m field strength based on Alan=92s assumptions.

= =A0

= G3XBM=92s signals at 14.9km measured= -42.5dB which is approximately 100uV/m.=A0 Assuming= 100mV/m at 10km equals 1W ERP, then 64mV/m would equal 1W ERP at= 14.9kms (approximately 4dB weaker signal from the CCIR curves). The ERP is lower by the ratio of 100uV/m to 64mV/m. So, my ERP in the best direction is 56dB= down on 1W, which is 2.5uW ERP.

= =A0

= If this calculation is correct then= I=92m surprised that such a low power (2W from PA) into such a strange antenna structure (20m separated ground= rods connected by wire just 1.5m above ground for most of the run) can produce= so much ERP.

= =A0

= Please can you check these figures= Alan (or others) and see if you agree?


73s
Roger G3XBM

--
ht= tp://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm G3XBM=A0=A0 GQRP 1678=A0=A0=A0 ISWL G11088
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