Return-Path: Received: from mtain-de04.r1000.mx.aol.com (mtain-de04.r1000.mx.aol.com [172.29.64.204]) by air-ma06.mail.aol.com (v129.4) with ESMTP id MAILINMA063-b52a4d77acae3de; Wed, 09 Mar 2011 11:37:02 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-de04.r1000.mx.aol.com (Internet Inbound) with ESMTP id E6FF138000103; Wed, 9 Mar 2011 11:37:00 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PxMMd-0000aD-85 for rs_out_1@blacksheep.org; Wed, 09 Mar 2011 16:35:55 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PxMMc-0000a4-Fe for rsgb_lf_group@blacksheep.org; Wed, 09 Mar 2011 16:35:54 +0000 Received: from smtpa1.mediabeam.com ([194.25.41.13]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PxMMa-0005fr-3F for rsgb_lf_group@blacksheep.org; Wed, 09 Mar 2011 16:35:54 +0000 Received: from UMS02-SMTP3 (balancer04.mediabeam.com [10.100.1.40]) by smtpa1.mediabeam.com (8.13.8/8.13.1) with ESMTP id p29GZkKk021751 for ; Wed, 9 Mar 2011 17:35:46 +0100 From: uwe-jannsen@kabelmail.de To: rsgb_lf_group@blacksheep.org Message-ID: Date: Wed, 09 Mar 2011 17:35:46 +0100 X-Priority: 3 (Normal) MIME-Version: 1.0 X-Spam-Score: 0.6 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,NO_REAL_NAME=0.55 Subject: Re: VLF: ERP calculation (was: dj8wx on 8970.022Hz) Content-Type: multipart/alternative; boundary="----908FDC6C0F344A18860325E8B23894A3" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.6 required=5.0 tests=HTML_40_50,HTML_MESSAGE, NO_REAL_NAME,PRIORITY_NO_NAME 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: 3039ac1d40cc4d77acac4025 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) ------908FDC6C0F344A18860325E8B23894A3 Content-Type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable Hi Markus,=20 thanks for your instructions.=20 Ill try this substitute mothode one hot day in the month of august.=20 Thanks for the link to the US grabber.=20 vy 73=20 Uwe/dj8wx=20 Von: rsgb_lf_group@blacksheep.org Gesendet: 08.03.2011 20:33 An: rsgb_lf_group@blacksheep.org Betreff: VLF: ERP calculation (was: dj8wx on 8970.022Hz) Dear Uwe, LF,=20 my usual method=A0for ERP measurement is as follows:=20 1. Build a simple nonresonant loop of known area A, eg. 50 cm x 50 cm x 4= turns =3D 1 m^2. Do not connect a capacitor.=20 2. Using a selective voltmeter or=A0soundcard, measure the voltage Vloop= induced by a strong transmitter in the far field (eg. DHO). Note that the= main Marconi antenna should be disconnected (ie. grounded via 1 megohm)= during this measurement to decouple it from=A0the loop.=20 3. Calculate the magnetic fieldstrength B=A0(for DHO) using Faraday's indu= ction law:=20 =A0 B =3D Vloop / A / omega=20 4. Derive the undisturbed electric field from this transmitter:=20 =A0 E =3D=A0Zo=A0* H =3D B * Zo=A0/ =B5o=A0=3D B * c=20 5. Series resonate your Marconi for DHO, connect a high impedance voltmete= r, and=A0measure the open circuit voltage Vmarconi.=20 7. Derive the effective height of the Marconi:=20 =A0 heff =3D Vmarconi / E=20 8. Calculate the radiation resistance at your transmit frequency:=20 =A0=A0Rrad =3D 1579 ohm * (heff / lambda)^2=20 9. Connect your TX and loading coil, measure the antenna current=A0I, eith= er at the cold end of the coil or in the ground line, and calculate radiat= ed power:=20 =A0 EMRP =3D Rrad * I^2=20 10: If you want, you can convert radiated power=A0to ERP referenced to a= halfwave dipole:=20 =A0 ERP =3D EMRP * 1.83=20 You do not have to absolutely calibrate the voltmeter because the result= depends only the ratio between the loop and Marconi measurement. This is= handy with the soundcard, as you will only need=A0to read a=A0dB differen= ce.=20 The method also correctly includes the shunt effect of nearby objects (eg.= trees) on the radiated power. It measures the disturbed electrical field,= and compares it to a reference based on=A0the undisturbed magnetic=A0comp= onent.=20 Best 73,=20 Markus (DF6NM)=20 From: uwe-jannsen@kabelmail.de =20 Sent: Tuesday, March 08, 2011 7:27 PM=20 To: rsgb_lf_group@blacksheep.org =20 Subject: LF: VLF dj8wx on 8970.022Hz=20 Hi all,=20 Im doing some measurements trying to find out how low (high?) the ERP of= my system is.=20 the test lead of the oscilloscope in use has a resistor of 10Mohm. The osc= illoscope advise text says that I have to multiply the result by 10.=20 OK. I added two other 10Mohm=A0 in series multiplyed the result by 1000 an= d got 40000Vpp=20 using the twentieth of max TX power. 40kV? Is that possible?=20 the current from the coile foot into the radials was 0.145A (3 A with max= power). =20 I cant measure the Tesla voltage when the =A0power is raised because the= oscilloscope or other =20 instruments indicate results without connected to the object under test.= =20 the station is on the air in mode QRSS3600 on 8970.022Hz since today 1640U= TC.=20 current into the radials: one Ampere.=20 who will try to calculate the ERP?=20 the aerial in use can be seen at =20 http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm=A0=20 fourth pic on the site. The shown 23m long wire has been lengthened to 43m= .=20 best regards=20 Uwe/dj8wx ------908FDC6C0F344A18860325E8B23894A3 Content-Type: text/html; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable


Hi Markus,

 

thanks for your instructions.

 

Ill try this substitute mothode one hot day in the month of augus= t.

 

Thanks for the link to the US grabber.

 

vy 73

Uwe/dj8wx

 

 




Von: rsgb_lf_group@blacksheep.org
Gesendet: 08.03.2011 20:33
An: rsgb_lf_group@blacksheep.org
Betreff: VLF: ERP calculation (was: dj8wx on 8970.022Hz)

Dear Uwe, LF,
 
my usual method&= nbsp;for ERP measurement is as follows:
 
1. Build a simpl= e nonresonant loop of known area A, eg. 50 cm x 50 cm x 4 turns =3D 1 m^2. Do not connect a capacitor.<= /div>
2. Using a selec= tive voltmeter or soundcard, measure the voltage Vloop induced by a strong transmitter in the far field= (eg. DHO). Note that the main Marconi antenna should be disconnected (ie. groun= ded via 1 megohm) during this measurement to decouple it from the loop.
3. Calculate the= magnetic fieldstrength B (for DHO) using Faraday's induction law:
  B =3D Vlo= op / A / omega
4. Derive the un= disturbed electric field from this transmitter:
  E =3D&nbs= p;Zo * H =3D B * Zo / =B5o =3D= B * c
5. Series resona= te your Marconi for DHO, connect a high impedance voltmeter, and measure the open circuit voltage Vmarconi.
7. Derive the ef= fective height of the Marconi:
  heff =3D= Vmarconi / E
8. Calculate the= radiation resistance at your transmit frequency:
  Rrad= =3D 1579 ohm * (heff / lambda)^2
9. Connect your= TX and loading coil, measure the antenna current I, either at the cold end of the coil or in the groun= d line, and calculate radiated power:
  EMRP =3D= Rrad * I^2
10: If you want,= you can convert radiated power to ERP referenced to a halfwave dipole:
  ERP =3D= EMRP * 1.83
 
You do not have= to absolutely calibrate the voltmeter because the result depends only the ratio between the loop and= Marconi measurement. This is handy with the soundcard, as you will only need = to read a dB difference.
 
The method also= correctly includes the shunt effect of nearby objects (eg. trees) on the radiated power. It measures the distu= rbed electrical field, and compares it to a reference based on the undistu= rbed magnetic component.
 
Best 73,<= /div>
Markus (DF6NM)
 
From: uwe-jannsen@kabelmail.de=
Sent: Tuesday, March 08, 2011 7:27 PM
Subject:= LF: VLF dj8wx on 8970.022Hz

Hi all,
 
Im doing some measurements trying to= find out how low (high?) the ERP of my system is.
the test lead of the oscilloscope in= use has a resistor of 10Mohm. The oscilloscope advise text says that I have to multiply the= result by 10.
OK. I added two other 10Mohm = in series multiplyed the result by 1000 and got 40000Vpp
using the twentieth of max TX power.= 40kV? Is that possible?
the current from the coile foot into= the radials was 0.145A (3 A with max power).
I cant measure the Tesla voltage whe= n the  power is raised because the oscilloscope or other
instruments indicate results without= connected to the object under test.
 
the station is on the air in mode QR= SS3600 on 8970.022Hz since today 1640UTC.
 
current into the radials: one Ampere.
 
who will try to calculate the ERP?
the aerial in use can be seen at
 
fourth pic on the site. The shown 23= m long wire has been lengthened to 43m.
 
best regards
Uwe/dj8wx
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