X-GM-THRID: 1237857389972627748 X-Gmail-Labels: rsgb lf Delivered-To: daveyxm@gmail.com Received: by 10.78.172.1 with SMTP id u1cs178hue; Wed, 30 May 2007 01:13:20 -0700 (PDT) Received: by 10.66.249.16 with SMTP id w16mr407547ugh.1180512800113; Wed, 30 May 2007 01:13:20 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id 32si19888928nfu.2007.05.30.01.13.04; Wed, 30 May 2007 01:13:20 -0700 (PDT) Received-SPF: neutral (google.com: 193.82.116.20 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1HtJ8A-00061G-GG for rs_out_1@blacksheep.org; Wed, 30 May 2007 09:02:06 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1HtJ89-000617-TV for rsgb_lf_group@blacksheep.org; Wed, 30 May 2007 09:02:05 +0100 Received: from rutherford.zen.co.uk ([212.23.3.142]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1HtJ88-0003DH-WF for rsgb_lf_group@blacksheep.org; Wed, 30 May 2007 09:02:05 +0100 Received: from [82.68.18.174] (helo=acer5gi5q0ubzj) by rutherford.zen.co.uk with esmtp (Exim 4.50) id 1HtJ7u-0006Q4-Lg for rsgb_lf_group@blacksheep.org; Wed, 30 May 2007 08:01:51 +0000 From: "John W Gould" To: Date: Wed, 30 May 2007 09:01:41 +0100 Message-ID: <001e01c7a290$c67f99b0$0b01a8c0@acer5gi5q0ubzj> MIME-Version: 1.0 X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 In-Reply-To: <341873.21191.qm@web86408.mail.ird.yahoo.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 Importance: Normal X-Originating-Rutherford-IP: [82.68.18.174] X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: RE: Field Strength Meter Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01C7A299.284401B0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,HTML_FONTCOLOR_BLUE, 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 Status: O X-Status: X-Keywords: X-UID: 1470 This is a multi-part message in MIME format. ------=_NextPart_000_001F_01C7A299.284401B0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Chris, your experiments of measuring ERP are interesting. How close is = the result that you obtained with that derived from aerial modelling and = aerial current measurement? To what extent do you think that local = environmental factors can explain any differences? =20 I wouldn't be too concerned about leaving a 6dB margin. My off-the-cuff feeling is that so long as we make reasonable efforts in terms of = accuracy and can demonstrate an intent to operate within the -10dBW limit that = this should be acceptable to Ofcom. =20 =20 73 John, G3WKL =20 =20 -----Original Message----- From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of CHRISTOPHER = OSBORN Sent: 29 May 2007 21:05 To: LF group Subject: LF: Field Strength Meter This bank holiday I finished PA0SE's field strength meter (LF = Experimenter's Handbook) duly modified for 500 kc/s. I knocked up Helmholtz coils of almost identical proportions to those in Dick's published design and with these calibrated the F/S meter. Initial results look very promising and the meter seems quite linear up = to my calibrated maximum of 6 mV/m. This evening I trudged around the fields in Biggleswade making sundry readings, while my PC/TX put out a test signal every 3 minutes. If (?) my calculations are correct then I have an ERP of 40 mW averaged = over 3 (1 km distant) readings. I know this is not much of a sample but initial results are satisfactory = and fairly consistent. Apparently I am told that field strength measurement uncertainties are notoriously high - one RadCom informed letter suggests by as much as 6 = dB. If I wanted to be pedantic then presumably we should ensure that we = measure no more than 25 mW ERP to allow for the worst case uncertainty (tongue = in cheek!) 73 Chris G3XIZ _____ =20 Copy addresses and emails from any email account to Yahoo! Mail - quick, easy and free. Do it now... ------=_NextPart_000_001F_01C7A299.284401B0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
Chris,  your experiments of measuring ERP are = interesting.  How=20 close is the result that you obtained with that derived from aerial = modelling=20 and aerial current measurement?  To what extent do you think that = local=20 environmental factors can explain any differences?
 
I=20 wouldn't be too concerned about leaving a 6dB margin.  My = off-the-cuff=20 feeling is that so long as we make reasonable efforts in terms of = accuracy and=20 can demonstrate an intent to operate within the -10dBW limit that this = should be=20 acceptable to Ofcom. 
 
73=20 John, G3WKL
 
 
-----Original Message-----
From:=20 owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org]=20 On Behalf Of CHRISTOPHER OSBORN
Sent: 29 May 2007=20 21:05
To: LF group
Subject: LF: Field Strength=20 Meter

This bank holiday I finished PA0SE's field = strength=20 meter (LF Experimenter's Handbook) duly modified for 500 kc/s.

I = knocked=20 up Helmholtz coils of almost identical proportions to those in Dick's = published=20 design and with these calibrated the F/S meter.
Initial results look = very=20 promising and the meter seems quite linear up to my calibrated maximum = of =20 6 mV/m.

This evening I trudged around the fields in Biggleswade = making=20 sundry readings, while my PC/TX  put out a test signal every 3=20 minutes.
If (?) my calculations are correct then I have an ERP of 40 = mW=20 averaged over 3 (1 km distant) readings.
I know this is not much of a = sample=20 but initial results are satisfactory and fairly = consistent.

Apparently I=20 am told that field strength measurement uncertainties are notoriously = high - one=20 RadCom informed letter suggests by as much as 6 dB.
If I wanted to be = pedantic then presumably we should ensure that we measure no more than = 25 mW ERP=20 to allow for the worst case uncertainty (tongue in cheek!)

73 = Chris=20 G3XIZ






Copy addresses and emails from any email account to Yahoo! Mail - quick, = easy=20 and free. Do=20 it now... ------=_NextPart_000_001F_01C7A299.284401B0--