Return-Path: Received: from mtain-dk04.r1000.mx.aol.com (mtain-dk04.r1000.mx.aol.com [172.29.180.8]) by air-mc05.mail.aol.com (v129.10) with ESMTP id MAILINMC051-a9674dbd3550207; Sun, 01 May 2011 06:26:24 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk04.r1000.mx.aol.com (Internet Inbound) with ESMTP id F17EC380000AB; Sun, 1 May 2011 06:26:21 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QGTqJ-0001Zd-4a for rs_out_1@blacksheep.org; Sun, 01 May 2011 11:25:35 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QGTqI-0001ZU-J6 for rsgb_lf_group@blacksheep.org; Sun, 01 May 2011 11:25:34 +0100 Received: from mail-iw0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QGTqG-0005Jt-6l for rsgb_lf_group@blacksheep.org; Sun, 01 May 2011 11:25:34 +0100 Received: by iwn8 with SMTP id 8so6217940iwn.16 for ; Sun, 01 May 2011 03:25:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=HfAAIVLrHeG7gp38vjHR9DnDKLR0l910VoF1VT8udlo=; b=OIWbBzupyy/LRCwti2gesHIu/R6WqoRTukWnoEFDo2it1y/6FVJwkTBPd/IPwY7pEH mKGML+FXvJsJOikM6OnTQZDwS4Pion4kMCC8TaTYcRGwTR7tRQgXvDrWrZY4qjCSrZgl b9EF8PYdP5hp6EBo9ljJOhUKDKEBN3xXvN3jI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=hpD6hdRVM57MSDXbOK+2Edd8/9Lw8NEJU55e/Wgf+tWBpYYxMra0g72D47DbfvwPGl WnpEQ1rqcD3Dw3IG7t6pvG2ZGkpQGnFiJkzYf2AusSZvpdkZdqXEqXRfWmgUV49wzU7T zK0xdYYwjKYLbvQBrygM95tQAk2hkT5bHrKY8= MIME-Version: 1.0 Received: by 10.231.192.197 with SMTP id dr5mr5676796ibb.2.1304245525813; Sun, 01 May 2011 03:25:25 -0700 (PDT) Received: by 10.231.206.83 with HTTP; Sun, 1 May 2011 03:25:25 -0700 (PDT) In-Reply-To: <707765.95482.qm@web28101.mail.ukl.yahoo.com> References: <707765.95482.qm@web28101.mail.ukl.yahoo.com> Date: Sun, 1 May 2011 11:25:25 +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: Re: LF: ERP estimation Content-Type: multipart/alternative; boundary=0016e6d279f84418bf04a2345343 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-sid: 3039ac1db4084dbd354d1c8c X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016e6d279f84418bf04a2345343 Content-Type: text/plain; charset=ISO-8859-1 Yes - its called a calculator :-) and some measurement 'JNT On 1 May 2011 11:19, M0FMT wrote: > Hi Andy and LF > > There must be some software written that does this? > > 73 es GL Pete M0FMT IO91UX > > > ------------------------------ > *From:* Andy Talbot > > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Sun, 1 May, 2011 10:07:13 > *Subject:* LF: ERP estimation > > 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 >> >> >> >> > --0016e6d279f84418bf04a2345343 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Yes - its called a calculator=A0 :-)
and some measurement
=A0
'JNT


=A0
On 1 May 2011 11:19, M0FMT &l= t;m0fmt@yahoo.co.uk> wr= ote:
Hi Andy and LF
=A0
There must be some software written that does this?
=A0
73= es GL Pete M0FMT IO91UX=20

=
From: Andy Talbot <andy.g4jnt@gmail.c= om>=20

To:= rsgb_lf= _group@blacksheep.org
Se= nt: Sun, 1 May, 2011 10:07:13
Subject: LF: ERP estimatio= n

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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