Return-Path: Received: from rly-de02.mx.aol.com (rly-de02.mail.aol.com [172.19.170.138]) by air-de02.mail.aol.com (v123.4) with ESMTP id MAILINDE023-4bb49ff5ed8fc; Mon, 04 May 2009 17:32:38 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de02.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDE026-4bb49ff5ed8fc; Mon, 04 May 2009 17:32:10 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1M15lL-0007WO-Cq for rs_out_1@blacksheep.org; Mon, 04 May 2009 22:31:47 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1M15lK-0007WE-R3 for rsgb_lf_group@blacksheep.org; Mon, 04 May 2009 22:31:46 +0100 Received: from web28503.mail.ukl.yahoo.com ([87.248.110.182]) by relay1.thorcom.net with smtp (Exim 4.63) (envelope-from ) id 1M15lK-0003xL-46 for rsgb_lf_group@blacksheep.org; Mon, 04 May 2009 22:31:46 +0100 Received: (qmail 44362 invoked by uid 60001); 4 May 2009 21:31:40 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s1024; t=1241472700; bh=FFZZlotCXs+73lXQd4PgzIpK0WdGrvhNj8Tscau1sbM=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=LkinITf0SoixzDaztJ7jxuADi+oSqs7x6+ag6S/nTlH6/BV8P6vpZWhkFeqeiPLfc7FLHtPNrec7+lZDm5KOycjLlpj5WsyUALkweFoD5Kxrb5toN8WxmODbaRlqigYxSPposnnA/ePDU3itHndxI7BUM3RKyUIdTTaMWckLnGw= DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.co.uk; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=UguUDcC1Wgdu65UfWSGlp/f/5ysOv124RwRaIsJVHbAkACS6YrbV6ULnrSr3ciorbDhSjR7CX0eUz9Gj+V2MnMyBGfZItoqqEqz+ndMWfNFZxE8kwCYKNbCqTbOK2orL5rKzQ7DN2JS6FLcdOrar8mPfZKhMDD8z4JCKo5+I6hk=; Message-ID: <797428.43044.qm@web28503.mail.ukl.yahoo.com> X-YMail-OSG: oRQfpg0VM1mm6VJBuSZQ.jL41QNeCxMNcUUmsEfR2SikOc9B1oRdvcHF Received: from [80.6.43.68] by web28503.mail.ukl.yahoo.com via HTTP; Mon, 04 May 2009 21:31:40 GMT X-Mailer: YahooMailRC/1277.35 YahooMailWebService/0.7.289.1 References: <260286.17766.qm@web28508.mail.ukl.yahoo.com> <8bf118410905040810m1fb41016pab9a1c0a7c79bf06@mail.gmail.com> <106017.93017.qm@web28508.mail.ukl.yahoo.com> <109DCE3D58BE4C3DAD93CFE7859DA29B@AGB> Date: Mon, 4 May 2009 21:31:40 +0000 (GMT) From: Chris Osborn To: rsgb_lf_group@blacksheep.org In-Reply-To: <109DCE3D58BE4C3DAD93CFE7859DA29B@AGB> MIME-Version: 1.0 X-Karma: unknown: DomainKey-Status: good (testing) Subject: LF: Field Strength Meter - advice needed Content-Type: multipart/alternative; boundary="0-1728732408-1241472700=:43044" 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-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m240.2 ; domain : yahoo.co.uk DKIM : pass --0-1728732408-1241472700=:43044 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable No Graham, I can swap a flat battery with a new one and the output hardly moves. Yes the oscillator and RF stages are regulated and holding constant. The problem's before the mixer. As advised, I disconnected the RF stage and injected a signal into the mixer and it gives a constant output even with a blow heater playing on the=20= insides. 73 Chris XIZ ________________________________ From: Graham To: rsgb_lf_group@blacksheep.org Sent: Monday, 4 May, 2009 21:31:37 Subject: Re: LF: Field Strength Meter - advice needed Chris =20 Its not the battery is it ... assume=20 the supply voltage / regulated voltage is holding =20 constant ? =20 G ..=20 =20 From: Chris Osborn=20 Sent: Monday, May 04, 2009 9:23 PM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: Field Strength Meter - advice needed Thanks again Dave and Alan, I've spent a few more hours on the F/S=20 meter today and still have not found the problem. I can blow with a drinking=20 straw on any component and=20 there's very little output change yet with time there's a slow drift with=20 temperature - the output goes up with increased temperature. I thought=20 I'd found the problem as by squeezing the ferrite rod 's screening tube I=20 could get a fair change in the output (about 10 %). The tube's metal is not=20 aluminium but I guess an aluminium alloy. In any case I changed it for a=20 proper aluminium tube - no difference ! >From the shack's temperature=20 of 23 degrees and taking the F/S meter outside to an ambient=20 13=20 degrees the meter's output changed from 0.48 volts to 0.35 volts=20 !! I have run out of ideas now and am thinking maybe it's even the=20 permeability of the die cast box that's changing or maybe the perspex end=20 caps of the ferrite rod. . . . I'm getting desperate ! 73 Chris=20 G3XIZ ________________________________ From: Dave Pick=20 To: rsgb_lf_group@blacksheep.org Sent: Monday, 4 May, 2009=20 16:10:26 Subject: Re: LF: Field=20 Strength Meter - advice needed Chris Have you tried a can=20 of "freezer" spray to identify where the problem lies? Is it the ferrite aer= ial=20 or is it the FET amplifier? If you have enough gain then a little negative=20 feedback on the FET stage may help, add some un-decoupled source=20 resistor. Dave 'YXM 2009/5/3 Chris Osborn LF, I've just rebuilt PA0SE's field strength meter (LF Experimenters' Handbook)= , modified for use on the 500 kHz band. I've followed the published circuit as near as possible considering availab= le components, the differences being: a) I have used a small variable capacitor instead of the published varicaps= . b) I used a JFET 2N3819 in the front end instead of dual gate mosfets. c) Obviously I now use the MW coil of the ferrite rod instead of the publis= hed LW coil. I have made a decent Helmholtz coil which gives a stable magnetic field yet= the=20 field strength meter's output voltage is very dependent on temperature and=20= can vary up to 30 %. I would be most grateful for any advice on curing this problem as I've spen= t hours trying to correct it. 73 Chris G3XIZ --=20 G3YXM IO92BK Birmingham UK ________________________________ =20 No virus found in this incoming message. Checked by AVG - www.avg.com=20 Version: 8.5.287 / Virus Database: 270.12.17/2095 - Release=20 Date: 05/04/09 06:00:00 =20 --0-1728732408-1241472700=:43044 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
No Graham,

I can swap a flat battery with a new one a= nd the output hardly moves.
Yes the oscillator and RF stages are regulate= d and holding constant.

The problem's before the mixer.
As advised= ,  I disconnected the RF stage and injected a signal into the
mixer=20= and it gives a constant output even with a blow heater playing on the inside= s.

73 Chris XIZ


From: Graham <g8fzk@g8fzk.fsnet.co.uk>
To: rsgb_lf_group@blacksheep.org
Sent: Monday, 4 May, 2009 21:31:37
= Subject: Re: LF: Field Strengt= h Meter - advice needed

=20
Chris
 
Its not the  battery is it ... ass= ume=20 the  supply  voltage / regulated voltage  is holding =20 constant ?
 
G ..
 

Sent: Monday, May 04, 2009 9:23 PM
Subject: LF: Field Strength Meter - advice needed

Thanks again Dave and Alan,

I've spent a few more hours on the F= /S=20 meter today and still have not found the problem.
I can blow with a drink= ing=20 straw on any component an= d=20 there's very little
output change yet with time there's a slow drift with= =20 temperature - the output goes up
with increased temperature.

I tho= ught=20 I'd found the problem as by squeezing the ferrite rod 's screening tube
I= =20 could get a fair change in the output (about 10 %).
The tube's metal is n= ot=20 aluminium but I guess an aluminium alloy.
In any case I changed it for a=20 proper aluminium tube - no difference !

From the shack's temperature=20 of  23 degrees and taking the F/S meter outside to an ambient
13=20 degrees the meter's output changed from  0.48 volts to 0.35 volts=20 !!

I have run out of ideas now and am thinking maybe it's even the=20 permeability of the die cast box
that's changing or maybe the perspex end= =20 caps of the ferrite rod. . . . I'm getting desperate !

73 Chris=20 G3XIZ

From: Dave Pick=20 <daveyxm@googlemail.com>
To:<= /span>=20 rsgb_lf_group@blacksheep.org
Sent:<= /span> Monday, 4 May, 2009=20 16:10:26
Subject: Re: LF= : Field=20 Strength Meter - advice needed

Chris

Have you tried a c= an=20 of "freezer" spray to identify where the problem lies? Is it the ferrite aer= ial=20 or is it the FET amplifier? If you have enough gain then a little negative=20 feedback on the FET stage may help, add some un-decoupled source=20 resistor.

Dave 'YXM

2009/5/3 Chris Osborn <g3xiz@yahoo.co.uk>
LF,

I've just rebuilt PA0SE's field strength meter (LF=20 Experimenters' Handbook),
modified for use on the 500 kHz band.

= I've=20 followed the published circuit as near as possible considering available=20 components,
the differences being:
a) I have used a small variable=20 capacitor instead of the published varicaps.
b) I used a JFET 2N3819 in= the=20 front end instead of dual gate mosfets.
c) Obviously I now use the MW c= oil=20 of the ferrite rod instead of the published LW coil.

I have made a=20 decent Helmholtz coil which gives a stable magnetic field yet the
fiel= d=20 strength meter's output voltage is very dependent on temperature and can v= ary=20 up to
30 %.

I would be most grateful for any advice on curing th= is=20 problem as I've spent hours trying
to correct it.

73 Chris=20 G3XIZ







--
G3YXM IO92BK Birmingham UK


No virus found in this incoming message.
Checked by AVG=20= -=20 www.avg.com
= Version: 8.5.287 / Virus Database: 270.12.17/2095 - Release=20 Date: 05/04/09 06:00:00

--0-1728732408-1241472700=:43044--