Return-Path: Received: from rly-mc01.mx.aol.com (rly-mc01.mail.aol.com [172.21.164.85]) by air-mc07.mail.aol.com (v125.7) with ESMTP id MAILINMC071-d534accf855112; Wed, 07 Oct 2009 16:22:12 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-mc01.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMC013-d534accf855112; Wed, 07 Oct 2009 16:21:44 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Mvd0R-0000av-Gj for rs_out_1@blacksheep.org; Wed, 07 Oct 2009 21:21:03 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Mvd0Q-0000am-TC for rsgb_lf_group@blacksheep.org; Wed, 07 Oct 2009 21:21:02 +0100 Received: from smtp-out.globalstar.com ([206.220.220.205] helo=gwia.corp.globalstar.com) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Mvd0E-0007BR-Ds for rsgb_lf_group@blacksheep.org; Wed, 07 Oct 2009 21:20:53 +0100 Received: from dom-mlpx-MTA by gwia.corp.globalstar.com with Novell_GroupWise; Wed, 07 Oct 2009 13:20:41 -0700 Message-Id: <4ACCBFC9.8A4E.00FD.0@globalstar.com> X-Mailer: Novell GroupWise Internet Agent 7.0.3 Date: Wed, 07 Oct 2009 13:20:25 -0700 From: "David Weinreich" To: References: <57a24ca70910070818o2e4adde4k1c8daa318eb2eb30@mail.gmail.com> <006001ca4763$a69a1290$0301a8c0@mal769a60aa920> <002601ca4766$1ff29bb0$6c01a8c0@DELL4> <4ACCD7FA.5080501@ukonline.co.uk> <4ACCB110.8A4E.00FD.0@globalstar.com> In-Reply-To: Mime-Version: 1.0 X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,HTML_TAG_EXIST_TBODY=0.126 Subject: Re: LF: Re Propagation report Content-Type: multipart/alternative; boundary="=__Part0F248419.0__=" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.3 required=5.0 tests=EXCUSE_16,HTML_MESSAGE, HTML_TAG_EXISTS_TBODY 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-IP: 193.82.116.20 --=__Part0F248419.0__= Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Jim, =20 Thanks very much for the explanation it's very helpful. Too bad there aren= 't very many calibrated receivers and antennas. =20 73, =20 David Weinreich WA2VUJ/3 >>>=20 From: "James Moritz" To: Date: 10/07/09 4:02 PM Subject: Re: LF: Re Propagation report Dear David, LF Group, There are basically two ways of determining ERP, briefly: Method 1 is to calculate the radiation resistance (Rrad) of your antenna,= =20 which can be done using various text-book formulae, or using antenna=20 simulation software like EZNEC or similar. Then you measure the RF current= =20 flowing in the antenna (Iant). The ERP is then Iant^2 x Rrad x 1.8 (1.8 is= =20 the directivity of electrically small vertical or loop antennas, which in= =20 practice is what all amateur 136kHz antennas are). Method 2 is to measure the field strength some km from the antenna. The ER= P=20 is then (E x d)^2 /49, where E is the field strength, d distance in metres= .=20 This requires a calibrated antenna and measuring receiver, so is more=20 complicated to do. Method 1 is simpler to do, but yields ERP results that tend to be lower th= an=20 those obtained by method 2. This is thought to be due to various combined= =20 environmental effects on the antenna, which are not accounted for in the= =20 simple calculation. So to get a more accurate and definitive figure, you= =20 need to do method 2, but as far as compliance with licence conditions is= =20 concerned, method 1 is a conservative way of checking. Good luck in your efforts! Cheers, Jim Moritz 73 de M0BMU ----- Original Message -----=20 but From: "David Weinreich" To: Sent: Wednesday, October 07, 2009 8:17 PM Subject: Re: LF: Re Propagation report Peter, As an interested observer from the other side of the pond, how do you=20 determine that you are close to the ERP limit?? I'd be interested in knowi= ng=20 as I am trying to do some pro-bono work for the ARRL on getting use of 137= =20 kHz here in the USA. Tnx & 73, David Weinreich WA2VUJ/3 The information contained in this e-mail message is confidential, intended= only for the use of the individual or entity named above. If the reader= of this e-mail is not the intended recipient, or the employee or agent re= sponsible to deliver it to the intended recipient, you are hereby notified= that any review, dissemination, distribution or copying of this communica= tion is strictly prohibited. If you have received this e-mail in error, pl= ease contact postmaster@globalstar.com=20 --=__Part0F248419.0__= Content-Type: text/html; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Content-Description: HTML
Jim,
 
Thanks very much for the explanation it's very helpful. Too bad there= aren't very many calibrated receivers and antennas.
 
73,
 
David Weinreich
WA2VUJ/3

>>>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Date: 10/07/09 4:02 PM
Subject: Re: LF:  Re Propagation report
Dear Davi= d, LF Group,

There are basically two ways of determining ERP, brief= ly:

Method 1 is to calculate the radiation resistance (Rrad) of you= r antenna,
which can be done using various text-book formulae, or usin= g antenna
simulation software like EZNEC or similar. Then you measure= the RF current
flowing in the antenna (Iant). The ERP is then Iant^2= x Rrad x 1.8 (1.8 is
the directivity of electrically small vertical= or loop antennas, which in
practice is what all amateur 136kHz antenn= as are).

Method 2 is to measure the field strength some km from the= antenna. The ERP
is then (E x d)^2 /49, where E is the field strength= , d distance in metres.
This requires a calibrated antenna and measuri= ng receiver, so is more
complicated to do.

Method 1 is simpler= to do, but yields ERP results that tend to be lower than
those obtain= ed by method 2. This is thought to be due to various combined
environm= ental effects on the antenna, which are not accounted for in the
simpl= e calculation. So to get a more accurate and definitive figure, you
ne= ed to do method 2, but as far as compliance with licence conditions is concerned, method 1 is a conservative way of checking.

Good luck= in your efforts!

Cheers, Jim Moritz
73 de M0BMU

----- Or= iginal Message -----
but From: "David Weinreich" <David.Weinreich@g= lobalstar.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wed= nesday, October 07, 2009 8:17 PM
Subject: Re: LF: Re Propagation report=


Peter,

As an interested observer from the other side of= the pond, how do you
determine that you are close to the ERP limit??= I'd be interested in knowing
as I am trying to do some pro-bono work= for the ARRL on getting use of 137
kHz here in the USA.

Tnx &a= mp; 73,

David Weinreich
WA2VUJ/3




The information contained in this e-mail message is confidential,=20 intended only for the use of the individual or entity named above.= If=20 the reader of this e-mail is not the intended recipient, or the empl= oyee=20 or agent responsible to deliver it to the intended recipient, you ar= e=20 hereby notified that any review, dissemination, distribution or copy= ing=20 of this communication is strictly prohibited. If you have received= this=20 e-mail in error, please contact postmaster@globalstar.com=20

--=__Part0F248419.0__=--