Return-Path: Received: from mtain-df02.r1000.mx.aol.com (mtain-df02.r1000.mx.aol.com [172.29.64.214]) by air-de06.mail.aol.com (v129.4) with ESMTP id MAILINDE062-5eb74c62bd5b2ce; Wed, 11 Aug 2010 11:10:19 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-df02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 25233380004C7; Wed, 11 Aug 2010 11:10:12 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OjCuN-0001yQ-G8 for rs_out_1@blacksheep.org; Wed, 11 Aug 2010 16:07:59 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OjCuM-0001yH-Vy for rsgb_lf_group@blacksheep.org; Wed, 11 Aug 2010 16:07:58 +0100 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OjCuI-0002nA-CI for rsgb_lf_group@blacksheep.org; Wed, 11 Aug 2010 16:07:58 +0100 Received: from smtps02.kuleuven.be (smtpshost02.kulnet.kuleuven.be [134.58.240.75]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 5FD577B8056 for ; Wed, 11 Aug 2010 17:07:39 +0200 (CEST) Received: from ICTS-S-HUB-N1.luna.kuleuven.be (icts-s-hub-n1.luna.kuleuven.be [10.112.9.11]) by smtps02.kuleuven.be (Postfix) with ESMTP id 4E017F3862 for ; Wed, 11 Aug 2010 17:07:39 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N1.luna.kuleuven.be ([10.112.9.11]) with mapi; Wed, 11 Aug 2010 17:07:39 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Wed, 11 Aug 2010 17:07:38 +0200 Thread-Topic: 136kHz ERP calculation (G3XBM's earth electrode antenna) Thread-Index: Acs5YSIRC3zYv9YsQDe+BPu0kgChBAABNmov 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: 136kHz ERP calculation (G3XBM's earth electrode antenna) Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C510AC52D85ICTSSEXC2CAlu_" 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, 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-sid: 3039ac1d40d64c62bd5413f2 X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C510AC52D85ICTSSEXC2CAlu_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Hello Roger, 2uW ERP for 2W RF input means an antenna efficiency of -60dB. Using a more conventional 136kHz antenna (toploaded vertical) in most case= s 1 to 10kW is needed to get 1W ERP, meaning an antenne efficiency of -30= to -40dB. This difference of 20 to 30dB seems acceptable to me. 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: woensdag 11 augustus 2010 16:22 Aan: rsgb_lf_group@blacksheep.org; Alan Melia Onderwerp: LF: 136kHz ERP calculation (G3XBM's earth electrode antenna) 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 10= km (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 thumbn= ail 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 ER= P is lower by the ratio of 100uV/m to 64mV/m. So, my ERP in the best direc= tion 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 pr= oduce so much ERP. Please can you check these figures Alan (or others) and see if you agree? 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_BF4A524700075746A6467658DFC7102C510AC52D85ICTSSEXC2CAlu_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Hello Roger,
 
2uW ERP for 2W RF input means an ant= enna efficiency of -60dB.
Using a more conventional 136kHz ant= enna (toploaded vertical) in most cases 1 to 10kW is needed to get 1W ERP,= meaning an antenne efficiency of -30 to -40dB.
This difference of 20 to 30dB seems= acceptable to me.
 
73, Rik  ON7YD - OR7T
 
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger= Lapthorn [rogerlapthorn@gmail.com]
Verzonden: woensdag 11 augustus 2010 16:22
Aan: rsgb_lf_group@blacksheep.org; Alan Melia
Onderwerp: LF: 136kHz ERP calculation (G3XBM's earth electrode ante= nna)

<= font size=3D"2">Background from Alan Melia.....

<= font size=3D"2"> 

=93Hi Roger you can calibrate your loop first us= ing 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 300m= V/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 calcul= ation.=94

<= font size=3D"2"> 

<= font size=3D"2">So, this afternoon I measured the str= ength 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 assumptio= ns.

<= font size=3D"2"> 

<= font size=3D"2">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 weake= r 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.

<= font size=3D"2"> 

<= font size=3D"2">If this calculation is correct then= I=92m surprised that such a low power (2W from PA) into such a strange an= tenna structure (20m separated ground rods connected by wire just 1.5m above ground for most of the run) can produce so muc= h ERP.

<= font size=3D"2"> 

<= font size=3D"2">Please can you check these figures Al= an (or others) and see if you agree?


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_BF4A524700075746A6467658DFC7102C510AC52D85ICTSSEXC2CAlu_--