Return-Path: Received: from mtain-dh06.r1000.mx.aol.com (mtain-dh06.r1000.mx.aol.com [172.29.65.26]) by air-de02.mail.aol.com (v129.4) with ESMTP id MAILINDE024-5ea94d7684ac2f4; Tue, 08 Mar 2011 14:34:04 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh06.r1000.mx.aol.com (Internet Inbound) with ESMTP id DA1D2380000A1; Tue, 8 Mar 2011 14:34:02 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Px2ec-0001UR-Ea for rs_out_1@blacksheep.org; Tue, 08 Mar 2011 19:33:10 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Px2eb-0001UI-Si for rsgb_lf_group@blacksheep.org; Tue, 08 Mar 2011 19:33:09 +0000 Received: from imr-da01.mx.aol.com ([205.188.105.143]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Px2eZ-0000el-AC for rsgb_lf_group@blacksheep.org; Tue, 08 Mar 2011 19:33:09 +0000 Received: from mtaout-db06.r1000.mx.aol.com (mtaout-db06.r1000.mx.aol.com [172.29.51.198]) by imr-da01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p28JWs7L019683 for ; Tue, 8 Mar 2011 14:32:54 -0500 Received: from White (nrbg-4dbfa1d0.pool.mediaWays.net [77.191.161.208]) by mtaout-db06.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 049F2E0000E8 for ; Tue, 8 Mar 2011 14:32:50 -0500 (EST) Message-ID: <825860A15E684FF9AC429E9DDFA8AA15@White> From: "Markus Vester" To: References: <33d07ccc43ec486d83d0d460928f26ad@kabelmail.de> Date: Tue, 8 Mar 2011 20:33:13 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: VLF: ERP calculation (was: dj8wx on 8970.022Hz) Content-Type: multipart/alternative; boundary="----=_NextPart_000_0004_01CBDDD0.0BF2D1F0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_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: 3039ac1d411a4d7684aa5c26 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_0004_01CBDDD0.0BF2D1F0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Dear Uwe, LF, my usual method for ERP measurement is as follows: 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. 2. Using a selective 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. grounded via 1= megohm) during this measurement to decouple it from the loop. 3. Calculate the magnetic fieldstrength B (for DHO) using Faraday's in= duction law: B =3D Vloop / A / omega 4. Derive the undisturbed electric field from this transmitter: E =3D Zo * H =3D B * Zo / =3D B * c 5. Series resonate your Marconi for DHO, connect a high impedance volt= meter, and measure the open circuit voltage Vmarconi. 7. Derive the effective 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, ei= ther at the cold end of the coil or in the ground 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 resu= lt depends only the ratio between the loop and Marconi measurement. Th= is is handy with the soundcard, as you will only need to read a dB dif= ference. The method also correctly includes the shunt effect of nearby objects= (eg. trees) on the radiated power. It measures the disturbed electric= al field, and compares it to a reference based on the undisturbed magn= etic component. Best 73, Markus (DF6NM) From: uwe-jannsen@kabelmail.de=20 Sent: Tuesday, March 08, 2011 7:27 PM To: rsgb_lf_group@blacksheep.org=20 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).=20 I cant measure the Tesla voltage when the power is raised because the= oscilloscope or other=20 instruments indicate results without connected to the object under tes= t. the station is on the air in mode QRSS3600 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=20 http://dj8wx-dl.de/hompage500kHz/TX%20equipment.htm=20 fourth pic on the site. The shown 23m long wire has been lengthened to= 43m. best regards Uwe/dj8wx=20 ------=_NextPart_000_0004_01CBDDD0.0BF2D1F0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Dear Uwe, LF,
 
my usual method for ERP measurem= ent is as=20 follows:
 
1. Build a simple nonresonant loop of= known area A,=20 eg. 50 cm x 50 cm x 4 turns =3D 1 m^2. Do not connect a capacitor.
2. Using a selective voltmeter or&nbs= p;soundcard,=20 measure the voltage Vloop induced by a strong transmitter in the far= field (eg.=20 DHO). Note that the main Marconi antenna should be disconnected (ie.= grounded=20 via 1 megohm) during this measurement to decouple it from the=20 loop.
3. Calculate the magnetic fieldstreng= th B (for=20 DHO) using Faraday's induction law:
  B =3D Vloop / A / omega=
4. Derive the undisturbed electric fi= eld from this=20 transmitter:
  E =3D Zo * H =3D B= * Zo /=20 =B5o =3D B * c
5. Series resonate your Marconi for= DHO, connect a=20 high impedance voltmeter, and measure the=20 open circuit voltage Vmarconi.
7. Derive the effective height of the= =20 Marconi:
  heff =3D Vmarconi / E
8. Calculate the radiation resistance= at your=20 transmit frequency:
  Rrad =3D 1579 ohm * (heff= /=20 lambda)^2
9. Connect your TX and loading coil,= measure the=20 antenna current I, either at the cold end of the coil or in the= ground=20 line, and calculate radiated power:
  EMRP =3D Rrad * I^2
10: If you want, you can convert radi= ated=20 power to ERP referenced to a halfwave dipole:
  ERP =3D EMRP * 1.83
 
You do not have to absolutely calibra= te the=20 voltmeter because the result depends only the ratio between the loop= and Marconi=20 measurement. This is handy with the soundcard, as you will only need&n= bsp;to=20 read a dB difference.
 
The method also correctly includes th= e shunt effect=20 of nearby objects (eg. trees) on the radiated power. It measures the= disturbed=20 electrical field, and compares it to a reference based on the und= isturbed=20 magnetic component.
 
Best 73,
Markus (DF6NM)
 
Sent: Tuesday, March 08,= 2011 7:27=20 PM
Subject: LF: VLF dj8wx= on=20 8970.022Hz

Hi all,
 
Im doing some measurements trying to find ou= t how low=20 (high?) the ERP of my system is.
the test lead of the oscilloscope in use has= a resistor=20 of 10Mohm. The oscilloscope advise text says that I have to multiply= the result=20 by 10.
OK. I added two other 10Mohm  in series= multiplyed=20 the result by 1000 and got 40000Vpp
using the twentieth of max TX power. 40kV?= Is that=20 possible?
the current from the coile foot into the rad= ials was=20 0.145A (3 A with max power).
I cant measure the Tesla voltage when the &n= bsp;power is=20 raised because the oscilloscope or other
instruments indicate results without connect= ed to the=20 object under test.
 
the station is on the air in mode QRSS3600= on 8970.022Hz=20 since today 1640UTC.
 
current into the radials: one=20 Ampere.
 
who will try to calculate the ERP?
the aerial in use can be seen at
 
fourth pic on the site. The shown 23m long= wire has been=20 lengthened to 43m.
 
best regards
Uwe/dj8wx
= ------=_NextPart_000_0004_01CBDDD0.0BF2D1F0--