Return-Path: Received: from mtain-mi06.r1000.mx.aol.com (mtain-mi06.r1000.mail.aol.com [172.21.131.164]) by air-db01.mail.aol.com (v129.4) with ESMTP id MAILINDB013-86434d07bb5134d; Tue, 14 Dec 2010 13:45:37 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mi06.r1000.mx.aol.com (Internet Inbound) with ESMTP id C427A380000B2; Tue, 14 Dec 2010 13:45:35 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PSZrl-0001dS-Tu for rs_out_1@blacksheep.org; Tue, 14 Dec 2010 18:44:49 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PSZrl-0001dJ-2p for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 18:44:49 +0000 Received: from imr-mb01.mx.aol.com ([64.12.207.164]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PSZrj-00069B-Fo for rsgb_lf_group@blacksheep.org; Tue, 14 Dec 2010 18:44:49 +0000 Received: from imo-da01.mx.aol.com (imo-da01.mx.aol.com [205.188.169.199]) by imr-mb01.mx.aol.com (8.14.1/8.14.1) with ESMTP id oBEIiU28007831 for ; Tue, 14 Dec 2010 13:44:30 -0500 Received: from MarkusVester@aol.com by imo-da01.mx.aol.com (mail_out_v42.9.) id l.fdc.833c4e2 (44223) for ; Tue, 14 Dec 2010 13:44:28 -0500 (EST) Received: from smtprly-dc01.mx.aol.com (smtprly-dc01.mx.aol.com [205.188.170.1]) by cia-dd08.mx.aol.com (v129.7) with ESMTP id MAILCIADD081-d1c64d07bb0514d; Tue, 14 Dec 2010 13:44:26 -0500 Received: from webmail-d088 (webmail-d088.sim.aol.com [205.188.181.43]) by smtprly-dc01.mx.aol.com (v129.5) with ESMTP id MAILSMTPRLYDC017-d1c64d07bb0514d; Tue, 14 Dec 2010 13:44:21 -0500 References: <80E0204D3E534137903FE0B8E499597F@IBM7FFA209F07C><4D0783FC.3090107@iup.uni-heidelberg.de> To: rsgb_lf_group@blacksheep.org Date: Tue, 14 Dec 2010 13:44:20 -0500 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: Markus Vester X-MB-Message-Type: User X-Mailer: AOL Webmail 32992-STANDARD Received: from 194.138.39.52 by webmail-d088.sysops.aol.com (205.188.181.43) with HTTP (WebMailUI); Tue, 14 Dec 2010 13:44:20 -0500 Message-Id: <8CD69D60DA867CF-130C-A2@webmail-d088.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: MarkusVester@aol.com X-Spam-Score: 0.3 (/) X-Spam-Report: autolearn=disabled,FORGED_AOL_TAGS=0.281,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: Earth Electrodes Content-Type: multipart/alternative; boundary="--------MB_8CD69D60E15E76B_130C_121_webmail-d088.sysops.aol.com" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=FORGED_AOL_TAGS,HTML_20_30, HTML_FONTCOLOR_UNKNOWN,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 x-aol-global-disposition: G x-aol-sid: 3039400cdece4d07bb4f6dd2 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ----------MB_8CD69D60E15E76B_130C_121_webmail-d088.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Dear Roger, Andy, interesting thread - let me state a few thoughts here: - as far as I understand, the purpose of the dual array at the Clam Lake= facility was to avoid the nulls in the coverage pattern. In effect, they= used two orthoganal loops fed in quadrature. - even at 76 Hz, the skin depth in ocean water is only about 26 meters. De= spite that the external noise is being attenuated as well, and that sensit= ive trailing receive antennas could have been employed, I still think that= the signaling was limited to a couple of hundred meters depth. =20 - the electromagnetic fields do not really propagate "through the earth",= at least not very far. The skin depth in "normal ground" at 9 kHz is only= a few tens of meters, and even low conductivity rock has a large attenuat= ion. The farfield radiation happens only by coupling of the subsurface cur= rent loop to propagating waves above ground. - in principle a wide spread array of transmitter stations could be used= to increase fieldstrangth at a given point. But if you start looking at= multiple wavelength arrays you will get unwanted directivity, and would= have to steer towards a single target receiver. A much more worthwile eff= ort would be a large receiver array. This can be easily done with small an= tennas, soundcard recording with GPS injection, data collection via intern= et, and a posteriori software focussing. One could even focus on multiple= transmitters simultaneously. Best regards, Markus (DF6NM) -----Urspr=C3=BCngliche Mitteilung-----=20 Von: Roger Lapthorn An: rsgb_lf_group@blacksheep.org Verschickt: Di., 14. Dez. 2010, 18:14 Thema: Re: LF: Earth Electrodes Andy, Surely two synchronised TX systems can only increase ERP by 3dB maximum?= ...or am I missing something? Yes, 600m baseline is similar to Sanguine pro rata with frequency and that= system got a megawatt TX output signal around the world and to a consider= able depth in the ocean with 100% reliability. Luckily we don't need to re= ach the ocean floors, so our ERP can be somewhat lower (!). A 600m baselin= e would not be that difficult to arrange for a portable test out in the co= untryside or across National Trust land or woodlands. 73s Roger G3XBM On 14 December 2010 16:54, Andy Talbot wrote: Google "Project Sanguine" =20 http://www.fas.org/nuke/guide/usa/c3i/fs_clam_lake_elf2003.pdf suggest= s more than 60km of cable used at 76Hz, so pro-rata not dissimiliar to 600= m earth spacing at 9kHz =20 However, they do use two synchronised transmitters, so the effective basel= ine becomes far greater. =20 =20 Now, how abot that for 8970Hz. Two stattion using low cost simple GPSDOs= and similar DDS / synthesizers can reasonably guarantee their respective= frequencies accuracy to 10^-9 short term At 10kHz (to keep numbers simpl= e), that is a differnece freq of no more than 10^-5, or 100000 seconds, or= one cycle in just over a day. And over this period, GPS derived sources= will average out as spot-on. =20 So, for low cost simple amateur coherent wide spaced VLF signalling freque= ncy is not an issue. SIgnal element timing can be synchronised to sub= microsecnds, again using GPS timing. =20 Maybe worth thinking about. Reading the posts so far, 'JNT interest coul= d be rekindled, so may yet apply for my NoV - although with a total house= plot of only some 25 x 7 metres, there not really any scope for Tx ante= nnas unless I use ground wires looping over the garden wall into and along= the road at the back =20 Andy www.g4jnt.com =20 =20 On 14 December 2010 16:27, Chris wrote: HiStefan, Yes, but 600m is VERY long! The wire even laying on the ground I would exp= ect to radiate quite well at 137 with that length! And how many watts?? ER= P?? I am sure 8970 would do well through the ground at the sort of powers bein= g spoken about. Probably ideal for submarines, as Roger says! Vy 73, Chris, G4AYT. ----- Original Message -----=20 From: Stefan Sch=C3=A4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 14, 2010 2:49 PM Subject: Re: LF: Earth Electrodes Hi Chris, But how do you explain that i have crossed 49.6 km with a 600m spaced eart= h electrode antenna on 8970 Hz? It was rather summer time than winther (re= garding QRN)! With the same antenna, my 137 kHz signal was seen 20 dB abov= e noise near Paris in DFCW-3!????? 73, Stefan Am 14.12.2010 15:15, schrieb Chris:=20 Hi Mal, Yes, that is what I had concluded years ago. No harm in trying though! Further to your previous e-mail to LF, looks to me like beacons are now be= coming the norm on 136/7kHz band and below. I have no problem with that pe= rsonally, indeed, I think it preferable to a QSO taking forever! I woud li= ke to see full idents though, no matter how slow. Vy 73, Chris, G4AYT. --=20 g3xbm-qrp.blogspot.com/ www.g3xbm.co.uk www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 ----------MB_8CD69D60E15E76B_130C_121_webmail-d088.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="utf-8"
Dear Roger, Andy,
 
interesting thread - let me state a few thoughts here:
 
- as far as I understand, the purpose of the dual array at the Clam= Lake facility was to avoid the nulls in the coverage pattern. In effect,= they used two orthoganal loops fed in quadrature.
 
- even at 76 Hz, the skin depth in ocean water is only abou= t 26 meters. Despite that the external noise is being= attenuated as well, and that sensitive trailing receive antennas could ha= ve been employed, I still think that the signaling was limi= ted to a couple of hundred meters depth.  
- the electromagnetic fields do not really propagate "through the ear= th", at least not very far. The skin depth in "normal ground" at 9 kHz is= only a few tens of meters, and even low conductivity rock has a larg= e attenuation. The farfield radiation happens only by coupling= of the subsurface current loop to propagating waves above ground.
 
- in principle a wide spread array of transmitter stations could be= used to increase fieldstrangth at a given point. But if you start looking= at multiple wavelength arrays you will get unwanted direct= ivity, and would have to steer towards a single target receiver.=  A much more worthwile effort would be a large receiver arr= ay. This can be easily done with small antennas, soundcard recording= with GPS injection, data collection via internet, and a posteriori softwa= re focussing. One could even focus on multiple transmitters= simultaneously.
Best regards,
Markus (DF6NM)

-----Urspr=C3=BCngliche Mitteilung-----
Von: Roger Lapthorn <rogerlapthorn@gmail.com>
An: rsgb_lf_group@blacksheep.org
Verschickt: Di., 14. Dez. 2010, 18:14
Thema: Re: LF: Earth Electrodes

Andy,

Surely two synchronised TX systems can only increase ERP by 3dB maximum?= ...or am I missing something?

Yes, 600m baseline is similar to Sanguine pro rata with frequency= and that system got a megawatt TX output signal around the world and to= a considerable depth in the ocean with 100% reliability. Luckily we don't= need to reach the ocean floors, so our ERP can be somewhat lower (!). A= 600m baseline would not be that difficult to arrange for a portable test= out in the countryside or across National Trust land or woodlands.

73s
Roger G3XBM

On 14 December 2010 16:54, Andy Talbot <andy.g4jnt@gmail.com> wrote:
Google "Project Sanguine"
 
  http://www.fas.org/nuke/guide/usa/c3i/fs_clam= _lake_elf2003.pdf   suggests more than 60km of cable us= ed at 76Hz, so pro-rata not dissimiliar to 600m earth spacing at 9kHz
 
However, they do use two synchronised transmitters, so the effective= baseline becomes far greater.  
 
Now, how abot that for 8970Hz.   Two stattion using low cos= t simple GPSDOs and similar DDS / synthesizers can reasonably guarantee th= eir respective frequencies accuracy to 10^-9 short term&nbs= p; At 10kHz (to keep numbers simple), that is a differnece freq of no= more than 10^-5, or 100000 seconds, or one cycle in just over a day. = ; And over this period, GPS derived sources will average out as spot-on.
 
So, for low cost simple amateur coherent wide spaced VLF signalling= frequency is not an issue.    SIgnal element timing can be= synchronised to sub microsecnds, again using GPS timing.
 
Maybe worth thinking about.   Reading the posts so far, 'JN= T interest could be rekindled, so may yet apply for my NoV - although with= a total house plot of only some 25 x  7  metres, there not real= ly any scope for Tx antennas unless I use ground wires looping over the ga= rden wall into and along the road at the back
 
Andy
www.g4jnt.com
 


 
On 14 December 2010 16:27, Chris = <c.ashby435@btinternet.com= > wrote:
HiStefan,
Yes, but 600m is VERY long! The wire even= laying on the ground I would expect to radiate quite well at 137 with tha= t length! And how many watts?? ERP??
I am sure 8970 would do well through= the ground at the sort of powers being spoken about. Probably ideal= for submarines, as Roger says!
Vy 73, Chris, G4AYT.
----- Original Message -----
Sent: Tuesday, December 14, 2010 2:= 49 PM
Subject: Re: LF: Earth Electrodes

Hi Chris,

But how do you explain that i have crossed 49.6 km with a 600m spaced eart= h electrode antenna on 8970 Hz? It was rather summer time than winther (re= garding QRN)! With the same antenna, my 137 kHz signal was seen 20 dB abov= e noise near Paris in DFCW-3!?????

73, Stefan


Am 14.12.2010 15:15, schrieb Chris:=20
Hi Mal,
Yes, that is what I had concluded years= ago. No harm in trying though!
Further to your previous e-mail to LF, lo= oks to me like beacons are now becoming the norm on 136/7kHz band and belo= w. I have no problem with that personally, indeed, I think it preferable= to a QSO taking forever! I woud like to see full idents though, no matter= how slow.
Vy 73,
Chris, G4AYT.




--
g3xbm-qrp.blogs= pot.com/
www.g3xbm.co.uk www.youtube.= com/user/g3xbm
G3XBM   GQRP= 1678    ISWL G11088
 ----------MB_8CD69D60E15E76B_130C_121_webmail-d088.sysops.aol.com--