X-GM-THRID: 1235778643069680522 X-Gmail-Labels: rsgb lf Delivered-To: daveyxm@gmail.com Received: by 10.78.172.1 with SMTP id u1cs162637hue; Mon, 7 May 2007 02:32:33 -0700 (PDT) Received: by 10.90.101.19 with SMTP id y19mr1760807agb.1178530352821; Mon, 07 May 2007 02:32:32 -0700 (PDT) Return-Path: Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mx.google.com with ESMTP id 20si6623387agd.2007.05.07.02.32.30; Mon, 07 May 2007 02:32:32 -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 1HkzVz-0000I7-LK for rs_out_1@blacksheep.org; Mon, 07 May 2007 10:28:19 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1HkzVz-0000Hw-3V for rsgb_lf_group@blacksheep.org; Mon, 07 May 2007 10:28:19 +0100 Received: from smtpout0190.sc1.he.tucows.com ([64.97.136.190] helo=n066.sc1.he.tucows.com) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1HkzVx-0003De-Pt for rsgb_lf_group@blacksheep.org; Mon, 07 May 2007 10:28:19 +0100 Received: from g3kev (62.252.228.63) by n066.sc1.he.tucows.com (7.2.069.1) id 4630CEE100046B8D for rsgb_lf_group@blacksheep.org; Mon, 7 May 2007 09:28:06 +0000 Message-ID: <002b01c7908a$06fcb5e0$3fe4fc3e@g3kev> From: "hamilton mal" To: References: <20070506130953.EF06D406C@mta-fe.casema.nl> Date: Mon, 7 May 2007 09:27:32 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: PA0SE FS meter Content-Type: multipart/alternative; boundary="----=_NextPart_000_0028_01C79089.F0D26CB0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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: 1844 This is a multi-part message in MIME format. ------=_NextPart_000_0028_01C79089.F0D26CB0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Dick Rollema=20 To: LF-Group=20 Sent: Sunday, May 06, 2007 1:09 PM Subject: LF: PA0SE FS meter To All from PA0SE There seems to be some interest to modify my design for a portable = field strength meter for use on 500 kHz. The instrument is described in = G3LDO's boek The LF Experimenters Handbook. But the circuit diagram has = some errors. The description can also be found at = http://www.veron.nl/tech/lf/fsm/pa0se.htm. Better use that one. I used a ferrite rod antenna from a transistor radio with its LW coil. = I expect the coil is too large for tuning the antenna circuit to 500 = kHz. You could try a MW coil or a LW coil with turns removed. The article also describes how the instrument can be calibrated using = a pair of Helmholtz coils. The coils are fed from a signal generator in = series with a 50 ohms resistor. I found that my coils have an inductance = of 1.2 microhenry. At 500 kHz that gives a reactance of 2.7 ohms. This can be completely be neglected against the 50 ohm resistor that = is in series with the reactance.. So the current through the coils is the generator output, divided by = 50 ohms. Note: the two coils are in parallel so each of them carries = half the current. The article describes how to handle this. One has to be careful about what the meter on the signal generator = indicates. On some models the meter indicates the EMF. When loaded with = a resistor equal to the internal resistance of the generator the output = voltage is half the EMF. But on other generators the meter indicates the voltage at the = terminals (potential difference) when the generator is loaded with a = resistor equal to the internal resistance of the generator. This PD is = taken as half the EMF. A simpler way to measure field strength is to use a single turn = untuned loop, connected to a calibrated selective voltmeter. I did it = that myself on 136 kHz after I was presented a Wandel & Goltermann = SPM-12 selective level meter that can also be run off a car battery. In a earlier e-mail to the reflector I included the equation that = gives the relation between the field strength and the voltage induced in = the loop. But my provider or the one of the reflector did not accept it because = the message "scored 5.8 spam points" as the Mail Administrated said. I had not realised I had used dirty words. Try again and leave certain words out hi If you have a receiver that covers 500 kHz, has an S-meter and can be = run off batteries you could use that with the single turn loop. But the S-meter must be calibrated first using a signal generator. 73, Dick, PA0SE=20 Hi Dick This is the method that I use, the tricky part is getting the loop = antenna calibrated accurately, more complicated than you think, for = absolute accuracy. ------=_NextPart_000_0028_01C79089.F0D26CB0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Dick=20 Rollema
Sent: Sunday, May 06, 2007 1:09 = PM
Subject: LF: PA0SE FS = meter

To All from PA0SE

There seems to be some interest to = modify my=20 design for a portable field strength meter for use on 500 kHz.  = The=20 instrument is described in G3LDO's boek The LF Experimenters = Handbook.=20 But the circuit diagram has some errors.
The description can also = be found=20 at http://www.veron.nl/tech/lf/fsm/pa0se.htm. = Better use=20 that one.

I used a ferrite rod antenna from a transistor radio = with its=20 LW coil. I expect the coil is too large for tuning the antenna circuit = to 500=20 kHz.
You could try a MW coil or a LW coil with turns = removed.

The=20 article also describes how the instrument can be calibrated using a = pair of=20 Helmholtz coils.  The coils are fed from a signal generator in = series=20 with a 50 ohms resistor. I found that my coils have an inductance of = 1.2=20 microhenry.  At 500 kHz that gives a reactance of 2.7 = ohms.
This can=20 be completely  be neglected against the 50 ohm resistor that is = in series=20 with the reactance..
So the current through the coils is the = generator=20 output, divided by 50 ohms. Note: the two coils are in parallel so = each of=20 them carries half the current.  The article describes how to = handle=20 this.

One has to be careful about what the meter on the signal=20 generator indicates. On some models the meter indicates the EMF. When = loaded=20 with a resistor equal to the internal resistance of the generator the = output=20 voltage is half the EMF.
But on other generators the meter = indicates the=20 voltage at the terminals (potential difference) when the = generator is=20 loaded with a resistor equal to the internal resistance of the=20 generator.  This PD is taken as half the EMF.

A simpler = way to=20 measure field strength is to use a single turn untuned loop, connected = to a=20 calibrated selective voltmeter. I did it that myself on 136 kHz after = I was=20 presented a Wandel & Goltermann SPM-12 selective level meter that = can also=20 be run off a car battery.
In a earlier e-mail to the reflector = I =20 included the equation that gives the relation between the field = strength and=20 the voltage induced in the loop.
But my provider or the one of the=20 reflector did not accept it  because the message "scored 5.8 spam = points"=20 as the Mail Administrated said.
I had not realised I had used dirty = words.
 
Try again and leave certain words out hi

If you have a = receiver=20 that covers 500 kHz, has an S-meter and can be run off batteries you = could use=20 that with the single turn loop.
But the S-meter must be calibrated = first=20 using a signal generator.

73, Dick, PA0SE
Hi Dick
This is the method that I use, the tricky part is getting the = loop=20 antenna calibrated accurately, more complicated than you think, for = absolute=20 accuracy.
 
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