Return-Path: Received: from mtain-dh03.r1000.mx.aol.com (mtain-dh03.r1000.mx.aol.com [172.29.65.23]) by air-mb07.mail.aol.com (v129.4) with ESMTP id MAILINMB074-a7a84c488c0e12f; Thu, 22 Jul 2010 14:21:02 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-dh03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 446B838000122; Thu, 22 Jul 2010 14:21:00 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Oc0N0-00024r-NB for rs_out_1@blacksheep.org; Thu, 22 Jul 2010 19:19:46 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Oc0N0-00024i-5S for rsgb_lf_group@blacksheep.org; Thu, 22 Jul 2010 19:19:46 +0100 Received: from cavuit02.kulnet.kuleuven.be ([134.58.240.44]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Oc0My-0000y0-OQ for rsgb_lf_group@blacksheep.org; Thu, 22 Jul 2010 19:19:46 +0100 Received: from smtps02.kuleuven.be (smtpshost02.kulnet.kuleuven.be [134.58.240.75]) by cavuit02.kulnet.kuleuven.be (Postfix) with ESMTP id D2568758A55 for ; Thu, 22 Jul 2010 20:19:35 +0200 (CEST) Received: from ICTS-S-HUB-N1.luna.kuleuven.be (icts-s-hub-n1.luna.kuleuven.be [10.112.9.11]) by smtps02.kuleuven.be (Postfix) with ESMTP id AE8C4F3862 for ; Thu, 22 Jul 2010 20:19:35 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N1.luna.kuleuven.be ([10.112.9.11]) with mapi; Thu, 22 Jul 2010 20:19:35 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Thu, 22 Jul 2010 20:19:35 +0200 Thread-Topic: VLF: Changes in MSK usage Thread-Index: AcspnTY0RlZRe9zNRZKp6sQCHiyikwAKPc7C Message-ID: References: <8CCF78D291F2FAB-A90-8915@webmail-m003.sysops.aol.com>, In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: RE: VLF: Changes in MSK usage Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C51094D0E59ICTSSEXC2CAlu_" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.0 required=5.0 tests=HTML_30_40,HTML_FONTCOLOR_BLUE, HTML_FONTCOLOR_UNKNOWN,HTML_MESSAGE,TO_ADDRESS_EQ_REAL 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: 3039ac1d41174c488c0c3415 X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C51094D0E59ICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Regarding Dave Gibson's thoughts on earth electrodes, I'm puzzled. As Stef= an says, the current is returned by a path within the soil/rock and a loop= MUST exist. Can the structure be modelled both as a magnetic loop and a= electric dipole? Hello Roger, simplified one could state that current causes a magnetic field and voltag= e causes a electric field. A small loop antenna is fed by a large current and small voltage and is co= nsidered to be "magnetic". A small vertical monopole (Marconi antenna) is fed by a large voltage and= small current and is considered to be "electric". But lots of antennas (in fact most antennas that are mot small in regard= with the wavelength) are fed by a significant current and voltage and can= be considered as partly "magnetic" and partly "electric". I believe that the same is true for an earth antenna. In regard with this a "mind game": Assume a small loop, fed at the center of one side but with a switch at th= e center of the opposite side. If the swithch is closed the antenna is small (magnetic) loop to be fed wi= th large current and small voltage. A series capacitor is needed to bring= this structure to resonance. If the switch is opened however the antenna becomes "electrical". It has= to be fed with a large voltage and small current. To bring it to resonanc= e a series inductor (loading coil) is needed. What if the switch is replace by an inductor, let's say with a value of ha= lf of the loading coil ? Now it is neither a magnetic loop neither a electric antenna, but somethin= g inbetween. It still need to be brought to resonance with a capacitor, but a much smal= ler value than needed for the pure loop. In regard with the pure loop the volatge at the feedingpoint will rise and= the current will sink. 73, Rik ON7YD - OR7T On 22 July 2010 09:15, Markus Vester > wrote: Dear VLF enthusiasts, browsing through saved VLF-grabber screenshots, I noticed some recent chan= ges of VLF MSK-band usage: 2010-06-24 06:00 20.27 kHz (ICV) QRT 2010-06-30 05:00 16.4 kHz (JXN) QRT 2010-07-05 07:05 18.3 kHz (HWU) QRT 2010-07-08 23:00 21.75 kHz (HWU) break for 6 hours 2010-07-10 06:00 22.1 kHz (GQD) switched from 100 bd to 200 bd 2010-07-10 10:00 19.58 kHz (GBZ) QRT Thus within a couple of weeks, half of the European military signals have= gone for good. Perhaps there is less need for submarine communications in today's world..= . let's hope that the submarines themselves (along with all that other mil= itary hardware) may become obsolete in tomorrow's world! 73, Markus (DF6NM) -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --_000_BF4A524700075746A6467658DFC7102C51094D0E59ICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Regarding Dave Gibson's thoughts on earth= electrodes, I'm puzzled. As Stefan says, the current is returned by a pat= h within the soil/rock and a loop MUST exist. Can the structure be modelle= d both as a magnetic loop and a electric dipole?
Hello Roger,

 

simplified one could state that curren= t causes a magnetic field and voltage causes a electric field.

A small loop antenna is fed by a large= current and small voltage and is considered to be "magnetic&quo= t;.

A small vertical monopole (Marconi ant= enna) is fed by a large voltage and small current and is considered to be= "electric".

But lots of antennas (in fact most ant= ennas that are mot small in regard with the wavelength) are fed by a= significant current and voltage and can be considered as partly "mag= netic" and partly "electric".

I believe that the same is true for an= earth antenna.

 

In regard with this a "mind game&= quot;:

Assume a small loop, fed at the center= of one side but with a switch at the center of the opposite side.<= /p>

If the swithch is closed the antenna= is small (magnetic) loop to be fed with large current and small volt= age. A series capacitor is needed to bring this structure to resonance.

If the switch is opened however the an= tenna becomes "electrical". It has to be fed with a large voltag= e and small current. To bring it to resonance a series inductor (loading= coil) is needed.

What if the switch is replace by an in= ductor, let's say with a value of half of the loading coil ?

Now it is neither a magnetic loop neit= her a electric antenna, but something inbetween.

It still need to be brought to resonan= ce with a capacitor, but a much smaller value than needed for the pure loo= p.

In regard with the pure loop the volat= ge at the feedingpoint will rise and the current will sink.

 

73, Rik  ON7YD - OR7T



On 22 July 2010 09:15, Markus Vester <markusvester@aol.com<= /a>> wrote:
Dear VLF enthusiasts,
 
browsing through saved VLF-grabber screenshots,= I noticed some recent changes of VLF MSK-band usage:
 
2010-06-24 06:00  20.27 kHz (ICV) QRT
2010-06-30 05:00  16.4 kHz (JXN) QRT
2010-07-05 07:05  18.3 kHz (HWU) QRT
2010-07-08 23:00  21.75 kHz (HWU) break for 6 hours
2010-07-10 06:00  22.1 kHz (GQD) switched from 100 bd to 200 bd
2010-07-10 10:00  19.58 kHz (GBZ) QRT
 
Thus within a couple of weeks, half of the Euro= pean military signals have gone for good.
 
Perhaps there is less need for submarine commun= ications in today's world... let's hope that the submarines themselves (al= ong with all that other military hardware) may become obsolete in tomorrow= 's world!
 
73, Markus (DF6NM)
 



--
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.u= k
http://www= .youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088
--_000_BF4A524700075746A6467658DFC7102C51094D0E59ICTSSEXC2CAlu_--