Return-Path: Received: from mtain-mj03.r1000.mx.aol.com (mtain-mj03.r1000.mail.aol.com [172.21.164.87]) by air-me02.mail.aol.com (v129.10) with ESMTP id MAILINME023-8ba64dbd23029f; Sun, 01 May 2011 05:08:18 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mj03.r1000.mx.aol.com (Internet Inbound) with ESMTP id B069438000089; Sun, 1 May 2011 05:08:16 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QGSce-0001EU-9X for rs_out_1@blacksheep.org; Sun, 01 May 2011 10:07:24 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QGScd-0001EL-Kd for rsgb_lf_group@blacksheep.org; Sun, 01 May 2011 10:07:23 +0100 Received: from mail-iy0-f171.google.com ([209.85.210.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QGScb-00044B-6H for rsgb_lf_group@blacksheep.org; Sun, 01 May 2011 10:07:23 +0100 Received: by iyi20 with SMTP id 20so6237245iyi.16 for ; Sun, 01 May 2011 02:07:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:date:message-id:subject:from:to :content-type; bh=xW2Wd4fzVFECPZJ+5tHXTlGDq+7jeQJgv+GrVO1tgQU=; b=i2A/7ZVDJLD+QMPf6H39dja1WaOqE4L3QYk4Fs27IMH2WAjTNmIkwRI0z03Edc7kSn zoxFxIPi7wRlXGUmKyh9s6qWX4KRUji1UaTwnGnTI9C+YNtwLIA931vviB2QO38Pfx8g Gs//Kehow5yoScBsIGKMbLKNfPqnZ8BXT+Vy0= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:date:message-id:subject:from:to:content-type; b=aFdoNlYkkU8+0nw2OSydUd2+j1FBfAiXH3EcPQGgs1PXUgmfQo6Lj8KS4rCA0/Tr6L fAZB11mxHG9KW538hqnsO6eCWgrnWOlFO0sBWYJd4M9dejI0ILzLyKHbDGs216jL7Wti 63U/Kn/Asr4xuTxkbBuHaqrQeQMrlvH73khvo= MIME-Version: 1.0 Received: by 10.42.246.129 with SMTP id ly1mr8084193icb.191.1304240833946; Sun, 01 May 2011 02:07:13 -0700 (PDT) Received: by 10.231.206.83 with HTTP; Sun, 1 May 2011 02:07:13 -0700 (PDT) Date: Sun, 1 May 2011 10:07:13 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: ERP estimation Content-Type: multipart/alternative; boundary=90e6ba3fd90b9be4fa04a2333b25 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 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-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m004.1 ; domain : gmail.com DKIM : fail x-aol-sid: 3039400c89a64dbd23002a9f X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --90e6ba3fd90b9be4fa04a2333b25 Content-Type: text/plain; charset=ISO-8859-1 You cannot calculate ERP directly from Transmit power without also obtaining an estimate of the additional losses, mainly caused by ground resistance. You must have either the RMS RF current in the vertical, OR teh total series loss resistance of the actual vertical system, before any Tx matching that may be in place. If you can measure RF current in the vertical, that will give you ERP directly from Ohms law on the Radiation resistance (which is directly related to the effective height of the antenna). ERP = I^2 * 3200 * (Heff / lambda) ^ 2 For a vertical with no top hat, Heff = half the effective height. If you were to have an infinite top hat, Heff = actual height. For most practical antennas use a value about half way, so a resonable approximation is given by : ERP = I^2 * 1600 * (H / lambda)^2 Another way is to measure your total load resistance in series with the antenna, = Rloss Once you have this value, the efficiency is then given by Radiation resistance / Rloss . Rrad ~= 1600 * (H/lambda)^2 as shown above. So ERP = Tx power * Rrad / Rloss Andy www.g4jnt.com On 30 April 2011 20:32, Luis EA3WX wrote: > Hi Dennis, > > A question, please. I am beaconing on 502,25 KHz. My transmitter puts 35 W > into a T antenna, high 20 m and an horizontal capacitor top of 10 m. > > With others ham fellows we are discussing what ERP I am sending, but we > have no results. Can you tell me how measure or are you calculating or > estimating this ERP? > > Thanks, 73 > > Luis, EA3WX > > *From:* DENNIS EASTERLING > *Sent:* Saturday, April 30, 2011 8:55 PM > *To:* rsgb_lf_group@blacksheep.org > *Subject:* LF: Re: GB4FPR 502 KHZ INTERNATIONAL MARCONI DAY 30/4/2011 > > Hi Graham > > I tried sending to you 1630-1635 and 1940-1945 local times today Saturday > 30 04 2011, but no reply. I guess you could not hear me, or I you. I > send CW 25watts into a 'T' aerial 20m top and 10m vertical. Estimated erp > 250mW max. Anyway, I hope you had a good day with plenty of DX. > > 73 Dennis M0JXM > > > > --90e6ba3fd90b9be4fa04a2333b25 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
You cannot calculate ERP directly from Transmit power without also ob= taining an estimate of the additional losses, mainly caused by ground resi= stance.=A0=A0 You must have either the RMS RF current in the vertical, OR= teh total series loss resistance of the actual vertical system,=A0before= any Tx matching that may be in place.
=A0
If you can measure RF current in the vertical, that will give you ERP= directly=A0from Ohms law on the=A0Radiation resistance (which is directly= related to=A0the effective height of the antenna).
=A0=A0=A0=A0 ERP =3D I^2 * 3200 * (Heff / lambda) ^ 2=A0=A0=A0=A0=A0=
For a vertical with no top hat, Heff =3D half the effective height.= =A0=A0
If you were to have an infinite top hat, Heff =3D actual height.=A0= =A0=A0
For most practical antennas use a value about half way, so a resonabl= e approximation is given by :
=A0=A0=A0=A0 ERP =3D I^2 * 1600 * (H / lambda)^2
=A0
Another way is to measure your total load resistance in series with= the antenna,=A0 =3D Rloss
Once you have this value, the efficiency is then given by Radiation= resistance / Rloss .=A0
Rrad ~=3D 1600 * (H/lambda)^2 as shown above.=A0 So ERP =3D=A0=A0 Tx= power * Rrad / Rloss
=A0
Andy


=A0
On 30 April 2011 20:32, Luis EA3WX <shekina1@orange.es>= wrote:
Hi Dennis,
=A0
A question, please. I am beaconing on 502,25 KHz. My transmitter puts= 35 W into a T antenna, high 20 m and an horizontal capacitor top of 10 m.=
=A0
With others ham fellows we are discussing what ERP I am sending, but= we have no results. Can you tell me how measure or are you calculating or= estimating this ERP?
=A0
Thanks, 73
=A0
Luis, EA3WX
=A0
Sent: Saturday, April 30, 2011 8:55 PM
Subject: LF: Re: GB4FPR 502 KHZ INTERNATIONAL MARCONI DAY 30/4= /2011
=A0
Hi Graham
=A0
I tried sending to you 1630-1635 and= 1940-1945 local times today Saturday 30 04 2011, but no reply.=A0=A0 I guess you could not hear me, or I you= .=A0=A0 I send CW 25watts into a 'T' aerial 20m top and 10m vertic= al.=A0=A0 Estimated erp 250mW max.=A0=A0 Anyway, I hope you had a good day= with plenty of DX.
=A0
73 Dennis M0JXM
=A0

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