Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w11MT4hl032625 for ; Thu, 1 Feb 2018 23:29:06 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ehNFz-0006bs-69 for rs_out_1@blacksheep.org; Thu, 01 Feb 2018 22:22:59 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ehNFx-0006bj-VC for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 22:22:57 +0000 Received: from resqmta-ch2-02v.sys.comcast.net ([2001:558:fe21:29:69:252:207:34]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ehNFt-00006K-9p for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 22:22:56 +0000 Received: from resomta-ch2-01v.sys.comcast.net ([69.252.207.97]) by resqmta-ch2-02v.sys.comcast.net with ESMTP id hNFTeOj6Kve36hNFpeGG4g; Thu, 01 Feb 2018 22:22:49 +0000 X-DKIM-Result: Domain=comcast.net Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcast.net; s=q20161114; t=1517523769; bh=QsyLW9CahA5CsYVabhcgTQ3ZFpt7oTimX40e339e6+0=; h=Received:Received:From:To:Subject:Date:Message-ID:MIME-Version: Content-Type; b=AV3IYB6gAwEyQqmq5fOQpRu/JXP8KH3XH8AgGq0cOzj5w6pyFOQTR9bSZ60DsT7fm lUjQ6eIuHtYPBp1LVh9SvFlpbXj1sAPgUPiYb6HlWSThVhllSUbXirhB7K6oCljXK1 x9j8DslOGaP+1alStqNbfT5vghprb6vNxodqUWWt7+hZ/x7AeL79NiIF2ouyGOoWNR 0AJyf3MPJlWqiZggyMlyMRxKc0BNdJIILUcpFAOHXkB+/2f8phUT3ANi4MS2eriUhD Ml4a0SwzLBJ1uHqNk1Lown+pMKUQkJIiX9Iq2kwDkrhO5McPTqtfegcoshqNW03XnR uVaxcX1fAgyRg== Received: from Owner ([IPv6:2601:140:8500:7f9f:78f6:dd:b547:d008]) by resomta-ch2-01v.sys.comcast.net with SMTP id hNFmeSHALNDORhNFneXyiZ; Thu, 01 Feb 2018 22:22:48 +0000 From: To: References: <579355A36AEE9D4FA555C45D556003AB9AB485D3@servigilant.vigilant.local> <5A7377F7.4050802@posteo.de> In-Reply-To: <5A7377F7.4050802@posteo.de> Date: Thu, 1 Feb 2018 17:22:25 -0500 Message-ID: <017101d39bab$2f0e3710$8d2aa530$@comcast.net> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQKIjaFcimWHhYva/6wQoj7d7es8IQKX8hVkohFjNaA= Content-Language: en-us X-CMAE-Envelope: MS4wfPVguUgLNt0B6jpuuHKi3MDo0FR/vATn7rU4N42Ajv/33g9ck1mS3lwysR77rPN100hJlxAGvfzBHzcX01maoDbwfDpMSMt44GwHqVqHcywHokbl1mN3 X3bWsbiyk/rmy5fKtFcqBzolufwAUWebAt4= X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Luis, Thank you for the underground mapping example; nice work by the speleo team. “As this is the near field it is supposed to work only at magnetic field due to the small size of the antenna ? So only magnetic field for underground signals at this distances ?” [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (hvanesce[at]comcast.net) 0.0 T_KAM_HTML_FONT_INVALID BODY: Test for Invalidly Named or Formatted Colors in HTML 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: a832015f9681fcc6d4e2835ba174a7e7 Subject: RE: LF: VLF Small magnetic antenna for Tx Content-Type: multipart/alternative; boundary="----=_NextPart_000_0172_01D39B81.46382F10" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.1 required=5.0 tests=HTML_30_40,HTML_MESSAGE, NO_REAL_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 This is a multipart message in MIME format. ------=_NextPart_000_0172_01D39B81.46382F10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Luis, =20 Thank you for the underground mapping example; nice work by the speleo = team. =20 =93As this is the near field it is supposed to work only at magnetic = field due to the small size of the antenna ? So only magnetic field for = underground signals at this distances ?=94 =20 At 38kHz the impedance of the transmitting loop=92s field at 100 meters = is ~ 25 ohms, which puts an optimized E-field (electric probe) receiver at perhaps a 45dB disadvantage, but your near-field intensity through 70 = meters of average-conductivity rock and 30 meters of air may be (based on your schematic and description) as much as 0.1 pT, so the E-field (electric probe) receiver will work well at 100 meters. =20 =20 =93Can we expect to receive the signal with an electric probe antenna in = the near field or the only chance is to be further away ? And then losing = the signal due to the distance =85.=94 =20 Based on your schematic and description: only in the near field.=20 At 1 km (and 38 kHz) and farther, any disadvantage of the E-field = (electric probe) receiver is small. At 1 km the near-field strength for the configuration that you described could be as much as ~ 1fT, so the near field component of the signal at = 1 km would be detectable (with significant integration time and/or low = noise), using an electric probe receiving antenna or a loop receiving antenna. But due primarily to the small aperture of the loop transmitting antenna that you described, the radiated field component at 1 km is far below = the threshold of detectability (perhaps 0.01 attotesla at 1km), so at = distances greater than a kilometer, the near field component fades below detectability, and the far-field component of the signal fades even = farther below the level of detectability. For most practical purposes, to be detected well into the far field, a = VLF loop transmitting antenna needs to be physically very large and driven = by more power than batteries can practically provide.=20 Note: the electric-probe antenna efficiently detects the radiated = component of the signal, and the radiated component of the signal decreases from = the transmitting antenna through the far field, so in outdoor above-ground (=93open field=94) VLF signal reception, moving an electric-probe = receiving antenna from a magnetic-loop transmitter=92s near field to its far field = never improves reception by a receiver with electric-probe antenna. =20 =20 =93What would be the radiated power of such antenna ?=94 =20 Based on your schematic and description, probably less than 100 pW. =20 Portable ULF and VLF loop transmitters are great for hundreds of meters through rock or air, but detection of ULF/VLF loop-transmitter signals = in the far field requires transmitting-antenna apertures that are = mechanically and electrically challenging in many independent ways =20 =20 Thank you for the underground mapping example; and best wishes to the = speleo team. I suppose it would be too complicated, but I wonder if they could correct their maps for angle-effects of air/rock conductivity = variations, if they monitored phase in addition to angle of arrival. =20 73, =20 Jim AA5BW =20 =20 =20 From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7FC Sent: Thursday, February 1, 2018 3:27 PM To: rsgb_lf_group@blacksheep.org Subject: Re: LF: VLF Small magnetic antenna for Tx =20 Hi Luis,=20 You seem to generate much activity on all bands in your Spanish region = :-) That is fine! Am 01.02.2018 19:58, schrieb VIGILANT Luis Fern=E1ndez:=20 =20 As this is the =93near field=94 it is supposed to work only at magnetic = field due to the small size of the antenna ? So only magnetic field for underground signals at this distances ? The E field also works in the near field of course but through the = ground you will have no chance with an underground E field TX antenna :-) Just = try it on LF at home :-) Can we expect to receive the signal with an electric probe antenna in = the near field or the only chance is to be further away ? In the moment i can receive my 970 Hz signal radiated from the E field antenna and received by the H field antenna. But it is not optimal. The signal strength will be higher when using the same type of antenna as = long as you are in a range of < 0.7 * far field distance. =20 Which would be the radiated power of such antenna ?=20 There are formulas on Rik's websites for 136 kHz, http://www.strobbe.eu/on7yd/136ant/#Loops 73, Stefan ------=_NextPart_000_0172_01D39B81.46382F10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Luis,

 

Thank = you for the underground mapping example; nice work by the speleo team. =

 

“As this is the near field it is supposed to = work only at magnetic field due to the small size of the antenna ? So = only magnetic field for underground signals at this distances = ?”

 

At 38kHz the impedance of the transmitting loop’s = field at 100 meters is ~ 25 ohms, which puts an optimized E-field = (electric probe) receiver at perhaps a 45dB disadvantage, but your = near-field intensity through 70 meters of average-conductivity rock and = 30 meters of air may be (based on your schematic and description) as = much as 0.1 pT, so the E-field (electric probe) receiver will work well = at 100 meters. =A0=A0=A0

 

“Can = we expect to receive the signal with an electric probe antenna in the = near field or the only chance is to be further away ?=A0 And then losing = the signal due to the distance ….”

 

Based on = your schematic and description: only in the near field. =

At 1 km = (and 38 kHz) and farther, any disadvantage of the E-field (electric = probe) receiver is small.

At 1 km the near-field strength for the configuration = that you described could be as much as ~ 1fT, so the near field = component of the signal at 1 km would be detectable (with significant = integration time and/or low noise), using an electric probe receiving = antenna or a loop receiving antenna.

But due primarily to the small aperture of the loop = transmitting antenna that you described, the radiated field component at = 1 km is far below the threshold of detectability (perhaps 0.01 attotesla = at 1km), so at distances greater than a kilometer, the near field = component fades below detectability, and the far-field component of the = signal fades even farther below the level of = detectability.

For most = practical purposes, to be detected well into the far field, a VLF loop = transmitting antenna needs to be physically very large and driven by = more power than batteries can practically provide. =

Note: = the electric-probe antenna efficiently detects the radiated component of = the signal, and the radiated component of the signal decreases from the = transmitting antenna through the far field, so in outdoor above-ground = (“open field”) VLF signal reception, moving an = electric-probe receiving antenna from a magnetic-loop = transmitter’s near field to its far field never improves reception = by a receiver with electric-probe antenna.

=A0=A0=A0=A0=A0=A0=A0=A0=A0

 

“What = would be the radiated power of such antenna ?”

 

Based on = your schematic and description, probably less than 100 = pW.

 

Portable = ULF and VLF loop transmitters are great for hundreds of meters through = rock or air, but detection of ULF/VLF loop-transmitter signals in the = far field requires transmitting-antenna apertures that are mechanically = and electrically challenging in many independent = ways

 

 

Thank = you for the underground mapping example; and best wishes to the speleo = team. I suppose it would be too complicated, but I wonder if they could = correct their maps for angle-effects of air/rock conductivity = variations, if they monitored phase in addition to angle of = arrival.

 

73,

 

Jim = AA5BW

 

 

 

From: owner-rsgb_lf_group@blacksheep.org = [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of = DK7FC
Sent: Thursday, February 1, 2018 3:27 = PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: = VLF Small magnetic antenna for Tx

 

Hi Luis, =

You seem to generate much activity on all bands in your Spanish = region :-) That is fine!

Am 01.02.2018 19:58, schrieb VIGILANT = Luis Fern=E1ndez:

 

As this is = the “near field” it is supposed to work only at magnetic = field due to the small size of the antenna ? So only magnetic field = for

underground signals at this = distances ?

The E = field also works in the near field of course but through the ground you = will have no chance with an underground E field TX antenna :-) Just try = it on LF at home :-)


Can we expect to receive the signal with an electric = probe antenna in the near field or the only chance is to be further away = ?

In the = moment i can receive my 970 Hz signal radiated from the E field antenna = and received by the H field antenna. But it is not optimal. The signal = strength will be higher when using the same type of antenna as long as = you are in a range of  < 0.7 * far field = distance.


 

Which would = be the radiated power of such antenna ?

There are formulas on Rik's websites for 136 kHz, http://www.strobbe.eu/= on7yd/136ant/#Loops

73, = Stefan

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