Return-Path: Received: from mtain-ma02.r1000.mx.aol.com (mtain-ma02.r1000.mx.aol.com [172.29.96.10]) by air-df07.mail.aol.com (v129.4) with ESMTP id MAILINDF074-5efd4d07825d3a3; Tue, 14 Dec 2010 09:42:37 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-ma02.r1000.mx.aol.com (Internet Inbound) with ESMTP id 913FB380000B5; Tue, 14 Dec 2010 09:42:35 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PSW4g-00065k-Kj for rs_out_1@blacksheep.org; Tue, 14 Dec 2010 14:41:54 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PSW4f-00065X-RL for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 14:41:53 +0000 Received: from mail-gx0-f170.google.com ([209.85.161.170]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PSW4d-00042Z-Aa for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 14:41:53 +0000 Received: by gxk20 with SMTP id 20so442077gxk.1 for ; Tue, 14 Dec 2010 06:41:45 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=XJJro+/aU5ViYVKKkuOKGbN3h/9zbnxYI0sFJZHOFGM=; b=BR0aM5mY0P/cuSS5uBa5rsCux26kY+eiKe0cvSHAExctFCXniPGlpbxfGY6MFGnWH7 oXSG8Hl2mkwYTbG6bmas0YCw7D3qEteuR7WDSEvTOGW0xoMnvltMoIyEf+WZiofXXGef dBPBrgsqibrwU81sfM55RE8OKwlHoF6/ZiCCc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=kVZeKaMKQwfnfcMTKhQ2H4W0GqWeaSAUk/5bYgjyBYV91L6crzJWxC7EECRt82Taym WoD0SnLvZmtYNRlh1o5v/N+Dv0tDdOu6o6OULpQp7UFuurT8GKkZ0wSVjgXefhYFYtsJ Ws7sNbf6bxS6TYmk1TiCBdrLgUFv9dzkkZNgM= MIME-Version: 1.0 Received: by 10.42.176.202 with SMTP id bf10mr4354594icb.184.1292337704748; Tue, 14 Dec 2010 06:41:44 -0800 (PST) Received: by 10.42.239.71 with HTTP; Tue, 14 Dec 2010 06:41:44 -0800 (PST) In-Reply-To: <001701cb9b95$a5dc1f10$0401a8c0@xphd97xgq27nyf> References: <612542AE1A3F497CB206279B0F0F8ECA@IBM7FFA209F07C> <001701cb9b95$a5dc1f10$0401a8c0@xphd97xgq27nyf> Date: Tue, 14 Dec 2010 14:41:44 +0000 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.3 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,MAILTO_TO_SPAM_ADDR=0.276 Subject: Re: LF: Re: Re: G3XBM - very long carrier VLF transmission test Dec 15th Content-Type: multipart/alternative; boundary=90e6ba6e83e6d247df04975fd1c9 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE, MAILTO_TO_SPAM_ADDR 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-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d262.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d600a4d07825b11cf X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --90e6ba6e83e6d247df04975fd1c9 Content-Type: text/plain; charset=ISO-8859-1 Chris/Mal et al, Certainly all my tests to date have been with what the US military calls "earth mode". This is propagation through the ground primarily by conduction and induction. What puzzles me, and some others, is that reception at a distance of 1 to 5.6km has been better using a loop antenna at the RX end rather than another pair of earth electrodes, suggesting the induction field is the stronger component. I am not an electromagnetic theory man and my physics is very rusty, so please excuse my ignorance here again. Mal is *partly *wrong about the use of earth electrodes. These have been used by the US military for VLF/ULF/ELF *radiated* communication with submarines worldwide. They have also been rejected as not secure enough for purely through-the-ground communications between buried bunkers because of the radiated component in the air! Where a very large "in the air" antenna structure is not practical, I suspect the results from an earth electrode are not that far down: on 136 and 500kHz even my small 20m spaced earth electrode antenna is less than 8dB down on the best "in the air" antenna I have so far managed to erect in my tiny plot of land. My unanswered questions are: 1. *Exactly what "helps" earth mode signals get as far as they do?* I find it amazing that just a few watts into my system is detected so well *so* far away (5.6km best DX, but further is certainly possible in some directions yet to be checked). 2. *How much signal is radiated in an earth mode set-up?* With a signal that is probably induced into overhead cables and conducted along miles of pipework and cables in the ground, railway tracks and even natural structures like water courses and rocks, then surely a tiny proportion *must * be radiated. OK the radiated signal may be minuscule, but we have already seen that with very slow QRSS and the power of Spectrum Lab and similar it is possible to detect these weak signals at a considerable distance. The attenuation of the radiated component is far less than the induction field component (6dB rather than 18dB attenuation for double distance I believe to a first order). *Does anyone know how to calculate the amount of RF radiatedin an earth electrode antenna * of given dimensions? 3. Assuming a very small amount of signal is radiated, *what are the limits for amateur communications using earth electrode structures*? With 100-200W and 600m long earth electrodes nearly 50km has already been achieved in Germany. So, OK I'll be very lucky to be heard more than 10km away by anyone on Wednesday, but I have already been surprised many times on VLF/LF and it is not totally beyond the bounds of possibility that, with QRSS6000 or similar, detection at a moderate distance may be possible with a stable signal source (mine is questionable I know) and suitable weak signal detection techniques. I continue to promote earth electrodes because, for me, they have worked. I do not deny that a large and well engineered vertical antenna would be better, but for many of us this is simply not an option. Investigations, and the fun, continue... 73s Roger G3XBM On 14 December 2010 13:48, mal hamilton wrote: > Chris > Generally speaking if you want to propagate a LF signal that covers > hundreds of Kilometres use an elevated Aerial and a good ground system. > The earth electrode TX and ground wires system is only intended for short > distances and received using the same method, howerver there will be > RF leakage and signals will also be copied at short distances using an > elevated aerial but maybe copied further afield when the TX station is using > several hundred watts or Kilowatts. > There is a lot of misleading and spectulative information about regarding > earth electrode antennas. What some are using for so called antennas I am > using as a ground for my elevated antennas. > g3kev > > > > ----- Original Message ----- > *From:* Chris > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Tuesday, December 14, 2010 12:18 PM > *Subject:* LF: Re: G3XBM - very long carrier VLF transmission test Dec > 15th > > Hi Roger, > I was under the impression that your earlier tests had shown that reception > from your earth electrodes at any distance was only possible by also using > earth electrodes. This suggests that those of us using an aerial stand > little or no chance, correct? > From what I recall of tests done forty or so years ago with friends, using > wideband audio into the ground, any form of 'in air' reception attempt was > seriously bad. The reception of a signal injected into the earth as the > conduction medium also required the receive system to be in the same medium > i.e. the earth. > Do prove me wrong...and good luck with the tests. > Vy 73, > Chris, G4AYT, Whitstable, Kent. > > ----- Original Message ----- > *From:* Roger Lapthorn > *To:* rsgb_lf_group@blacksheep.org ; Nick Swales ; Chris > Osborn ; Gary - G4WGT ; > vlf0308@abelian.org ; paula.taylor@metoffice.gov.uk > *Sent:* Sunday, December 12, 2010 10:51 PM > *Subject:* LF: G3XBM - very long carrier VLF transmission test Dec 15th > > This Wednesday, Dec 15th, I will run tests on *8.7608kHz* with very long > continuous TX periods of *several hours* interspersed with gaps of 0.5 to > 1 hour. Transmissions will start at 0900GMT and finish at 2300GMT. I will > reveal the TX pattern after the test so the test is done "blind". > > I'd be most grateful if suitably equipped stations could look for any > possible signs of the signal, even though I shall only be using the 20m > spaced earth electrodes and 5W as used for my local earthmode tests. Those > able to screw the bandwidths right down may just be able to detect > something, although I think it is unlikely at any great distance. > > *15.12.10 * > *0900-2300z * > *8.7608kHz * > *Carrier "on" periods of 30mins or more* > > Good luck to anyone having a go. > > 73s > Roger G3XBM > > -- > g3xbm-qrp.blogspot.com/ > www.g3xbm.co.uk > www.youtube.com/user/g3xbm > G3XBM GQRP 1678 ISWL G11088 > > -- g3xbm-qrp.blogspot.com/ www.g3xbm.co.uk www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --90e6ba6e83e6d247df04975fd1c9 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Chris/Mal et al,

Certainly all my tests to date have been with what= the US military calls "earth mode". This is propagation through= the ground primarily by conduction and induction. What puzzles me, and so= me others, is that reception at a distance of 1 to 5.6km has been better= using a loop antenna at the RX end rather than another pair of earth elec= trodes, suggesting the induction field is the stronger component. I am not= an electromagnetic theory man and my physics is very rusty, so please exc= use my ignorance here again.

Mal is partly wrong about the use of earth electrodes. These ha= ve been used by the US military for VLF/ULF/ELF radiated communicat= ion with submarines worldwide. They have also been rejected as not secure= enough for purely through-the-ground communications between buried bunker= s because of the radiated component in the air!

Where a very large "in the air" antenna structure is not pra= ctical, I suspect the results from an earth electrode are not that far dow= n: on 136 and 500kHz even my small 20m spaced earth electrode antenna is= less than 8dB down on the best "in the air" antenna I have so= far managed to erect in my tiny plot of land.

My unanswered questions are:

= 1. Exactly what "helps" earth mode signals get as far as they= do? I find it amazing that just a few watts into my system is detecte= d so well so far away (5.6km best DX, but further is certainly poss= ible in some directions yet to be checked).

2. How much signal is radiated in an earth mode set-up?= With a signal that is probably induced into overhead cables and conducted= along miles of pipework and cables in the ground, railway tracks and even= natural structures like water courses and rocks, then surely a tiny propo= rtion must be radiated. OK the radiated signal may be minuscule, bu= t we have already seen that with very slow QRSS and the power of Spectrum= Lab and similar it is possible to detect these weak signals at a consider= able distance. The attenuation of the radiated component is far less than= the induction field component (6dB rather than 18dB attenuation for doubl= e distance I believe to a first order). Does anyone know how to calcula= te the amount of RF radiated in an earth electrode antenna of= given dimensions?

3. Assuming a very small amount of signal is radiated, what are the= limits for amateur communications using earth electrode structures?= With 100-200W and 600m long earth electrodes nearly 50km has already been= achieved in Germany.

So, OK I'll be very lucky to be heard more than 10km away by= anyone on Wednesday, but I have already been surprised many times on VLF/= LF and it is not totally beyond the bounds of possibility that, with QRSS6= 000 or similar, detection at a moderate distance may be possible with a st= able signal source (mine is questionable I know) and suitable weak signal= detection techniques.

I continue to promote earth electrodes because, for me, they have work= ed. I do not deny that a large and well engineered vertical antenna would= be better, but for many of us this is simply not an option.

Inves= tigations, and the fun, continue...

73s
Roger G3XBM



On 14 Dec= ember 2010 13:48, mal hamilton <g3kevmal@talktalk.net> wrote:
Chris
Generally speaking if you want to pro= pagate a LF=20 signal that covers hundreds of Kilometres use an elevated Aerial and a goo= d=20 ground system.
The earth electrode TX=A0and ground= wires=20 system=A0is only intended for short distances=A0and received=A0using=20 the same method, howerver there will be RF=A0leakage and signals will also= be=20 copied =A0at short distances using an elevated aerial but maybe copied=20 further afield=A0when the TX station is using several hundred watts or=20 Kilowatts.
=A0There is a lot of misleading and= spectulative=20 information about regarding earth electrode antennas. What some are using= for so=20 called antennas I am using as a ground for my elevated antennas.
g3kev
=A0
=A0
----- Original Message -----
From:=20 Chris
Sent: Tuesday, December 14, 2010= 12:18=20 PM
Subject: LF: Re: G3XBM - very lo= ng=20 carrier VLF transmission test Dec 15th

Hi Roger,
I was under the impression that you= r earlier=20 tests had shown that reception from your earth electrodes at any distanc= e was=20 only possible by also using earth electrodes. This suggests that those= of us=20 using an aerial stand little or no chance, correct?
From what I recall of tests done fo= rty or so=20 years ago with friends, using wideband audio into the ground, any form= of 'in=20 air' reception attempt was seriously bad. The reception of a signal= injected=20 into the earth as the conduction medium also required the receive system= to be=20 in the same medium i.e.=A0the earth.
Do prove me wrong...and good luck= with the=20 tests.
Vy 73,
Chris, G4AYT, Whitstable, Kent.
----- Original Message -----
Sent: Sunday, December 12, 201= 0 10:51=20 PM
Subject: LF: G3XBM - very long= carrier=20 VLF transmission test Dec 15th

This Wednesday, Dec 15th, I will run tests on=20 8.7608kHz with very long continuous TX periods of several=20 hours interspersed with gaps of 0.5 to 1 hour. Transmissions will= start=20 at 0900GMT and finish at 2300GMT. I will reveal the TX pattern after= the=20 test so the test is done "blind".

I'd be most gra= teful if suitably=20 equipped stations could look for any possible signs of the signal, eve= n=20 though I shall only be using the 20m spaced earth electrodes and 5W as= used=20 for my local earthmode tests. Those able to screw the bandwidths right= down=20 may just be able to detect something, although I think it is unlikely= at any=20 great distance.

15.12.10=A0=A0=A0=A0=20
0900-2300z=A0
8.7608kHz=A0=A0=A0=20
Carrier "on" periods of 30mins or more

Good luck=20 to anyone having a go.

73s
Roger G3XBM

= --
g3xbm-= qrp.blogspot.com/
www.g3xbm.co.uk
www.youtub= e.com/user/g3xbm
<= /a>G3XBM=A0=A0 GQRP 1678=A0=A0=A0 ISWL=20 G11088



--
g3xbm-qrp.blogspot.com/
www.g3xbm.co.uk
= www.youtub= e.com/user/g3xbm
G3XBM=A0=A0 GQRP 1678= =A0=A0=A0 ISWL G11088
--90e6ba6e83e6d247df04975fd1c9--