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 w12APuc4002693 for ; Fri, 2 Feb 2018 11:25:59 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ehYMu-0000kD-DY for rs_out_1@blacksheep.org; Fri, 02 Feb 2018 10:14:52 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ehYMt-0000k4-JZ for rsgb_lf_group@blacksheep.org; Fri, 02 Feb 2018 10:14:51 +0000 Received: from mail-ot0-x22b.google.com ([2607:f8b0:4003:c0f::22b]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ehYMo-0001tX-V0 for rsgb_lf_group@blacksheep.org; Fri, 02 Feb 2018 10:14:50 +0000 Received: by mail-ot0-x22b.google.com with SMTP id a24so19786619otd.4 for ; Fri, 02 Feb 2018 02:14:45 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=gJrSO9/hdOPYAz0EsVhbHPQyWcgb5GuGyA8so7mRpNg=; b=NEhIxk86deHz8/WPKK3iiXW27Y8lOl2aw5BAomiIERQAga5XPrTqIVPScpvN4qgh14 rGxjybKzju8d7ZVQhLcwMqI25RWbSlFwcR/XE7UQ/cv0x14q9JvyOuwU1IgcdSLlpXNd 1McvcioNejIRz0dQtQOLya+O0ScKdpesPYSDv5RTSwq1F73OG7hOefNu6clHq2obvGDE yeLovznXFh+zWBc1g6ln+iFyaLxrmuPapIKKXdrYeB1lyZc72XLtwJuOhtBbezKkNnC2 OUxVXbicswvBRcY13gFGIPsBOSWWj629AvsiByElDfZKBfL3iegrRM+q2scrp1f3rRj7 WjGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=gJrSO9/hdOPYAz0EsVhbHPQyWcgb5GuGyA8so7mRpNg=; b=lHK2uyIDnnJNhzCyUK6mwefhtGANdDUQLuZAPM2AssGZFi5S/KHv9h99TI7sAiIJiV IawObjEDpRHjg5Kh/b28+xhyVFsZ+BYyfyMkYzwG+mnyWG78L4cAfjfdPdkcUrXaEmna 3ZKa6HmSZGq/wbAVnhu955R729wGMklk/uvjC2EKwKHfxAjVh6S7gCGtAZrc3o3xHteW HmqSuq0EuZ67zMeth908sDiWn89MVqq/bWsFRlVuBivbsRw3pmVn3+FjuOtYZmoFrmzy EHbri2bi/KS5f8ZlPVBEc7KrD8ZUWGex/K4T71PxeDXkylvW3sIlXXFyA4WOgzGubDZu 5Tkw== X-Gm-Message-State: AKwxyte9ekPJiATd2Jf3JS1rwfVmmsuY16ninkqp/ivazP8OKbeWvIIc tB1Oc7oZ++j7YxBuNekTR+0Qu71JRtt9VRaB9gcwddjL X-Google-Smtp-Source: AH8x225GwUij/pYpJAB3PBRv0ii5P1Zv/xbYzV0lIWDGqh9uzndL2QkBIWnCxJczQGr3ZDAOYYLsxyb/yeraaOTptsM= X-Received: by 10.157.14.45 with SMTP id c42mr12550224otc.59.1517566482207; Fri, 02 Feb 2018 02:14:42 -0800 (PST) MIME-Version: 1.0 Received: by 10.157.28.165 with HTTP; Fri, 2 Feb 2018 02:14:41 -0800 (PST) In-Reply-To: <017101d39bab$2f0e3710$8d2aa530$@comcast.net> References: <579355A36AEE9D4FA555C45D556003AB9AB485D3@servigilant.vigilant.local> <5A7377F7.4050802@posteo.de> <017101d39bab$2f0e3710$8d2aa530$@comcast.net> From: Roger Lapthorn Date: Fri, 2 Feb 2018 10:14:41 +0000 Message-ID: To: "rsgb_lf_group@blacksheep.org" 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: I am definitely NOT a theory man! However, I have had success on HF with ferrite rod antennas on TX and low power WSPR. Although inefficient, I often wonder if such a structure might have *some* place on lower bands as long as the ferrite rod does not saturate. Yes a decent BIG antenna will be much better. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (rogerlapthorn[at]gmail.com) 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: 77a0a2f41e380940c0e08c95737baa3b Subject: Re: LF: VLF Small magnetic antenna for Tx Content-Type: multipart/alternative; boundary="001a113e5374185945056437fbb3" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,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 --001a113e5374185945056437fbb3 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I am definitely NOT a theory man! However, I have had success on HF with ferrite rod antennas on TX and low power WSPR. Although inefficient, I often wonder if such a structure might have *some* place on lower bands as long as the ferrite rod does not saturate. Yes a decent BIG antenna will be much better. See https://sites.google.com/site/g3xbmqrp3/antennas/ferrite_tx 73s Roger G3XBM On 1 February 2018 at 22:22, wrote: > Luis, > > > > Thank you for the underground mapping example; nice work by the speleo > team. > > > > =E2=80=9CAs this is the near field it is supposed to work only at magneti= c field > due to the small size of the antenna ? So only magnetic field for > underground signals at this distances ?=E2=80=9D > > > > At 38kHz the impedance of the transmitting loop=E2=80=99s field at 100 me= ters 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 (electr= ic > probe) receiver will work well at 100 meters. > > > > =E2=80=9CCan we expect to receive the signal with an electric probe anten= na in the > near field or the only chance is to be further away ? And then losing th= e > signal due to the distance =E2=80=A6.=E2=80=9D > > > > 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 distanc= es > greater than a kilometer, the near field component fades below > detectability, and the far-field component of the signal fades even farth= er > below the level of detectability. > > For most practical purposes, to be detected well into the far field, a VL= F > 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 decreas= es > from the transmitting antenna through the far field, so in outdoor > above-ground (=E2=80=9Copen field=E2=80=9D) VLF signal reception, moving = an electric-probe > receiving antenna from a magnetic-loop transmitter=E2=80=99s near field t= o its far > field never improves reception by a receiver with electric-probe antenna. > > > > > > =E2=80=9CWhat would be the radiated power of such antenna ?=E2=80=9D > > > > 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 mechanical= ly > 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=C3=A1ndez: > > > > As this is the =E2=80=9Cnear field=E2=80=9D it is supposed to work only a= t 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 t= ry > 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 lon= g > 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 > --001a113e5374185945056437fbb3 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I am definitely NOT a theory man! However, I have had= success on HF with ferrite rod antennas on TX and low power WSPR. Although= inefficient, I often wonder if such a structure might have some pla= ce on lower bands as long as the ferrite rod does not saturate. Yes a decen= t BIG antenna will be much better.


=
73s
Roger G3XBM

On 1 February 2018 at 22:22, &l= t;hvanesce@comcas= t.net> wrote:

Luis,=

=C2= =A0

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

=C2=A0

=E2=80=9CAs this is the near field it is suppos= ed to work only at magnetic field due to the small size of the antenna ? So= only magnetic field for underground signals at this distances ?=E2=80=9D

<= /u>=C2=A0

At 38kHz t= he impedance of the transmitting loop=E2=80=99s 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 av= erage-conductivity rock and 30 meters of air may be (based on your schemati= c and description) as much as 0.1 pT, so the E-field (electric probe) recei= ver will work well at 100 meters. =C2=A0=C2=A0=C2=A0

=C2=A0

=E2= =80=9CCan we expect to receive the signal with an electric probe antenna in= the near field or the only chance is to be further away ?=C2=A0 And then l= osing the signal due to the distance =E2=80=A6.=E2=80=9D

<= p class=3D"MsoNormal">=C2=A0

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

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

At 1 km the near-field strength for the configuration that you described c= ould 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 detecta= bility (perhaps 0.01 attotesla at 1km), so at distances greater than a kilo= meter, the near field component fades below detectability, and the far-fiel= d component of the signal fades even farther below the level of detectabili= ty.

For most = practical purposes, to be detected well into the far field, a VLF loop tran= smitting 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 (=E2=80=9Copen field=E2=80=9D) VLF signal recept= ion, moving an electric-probe receiving antenna from a magnetic-loop transm= itter=E2=80=99s near field to its far field never improves reception by a r= eceiver with electric-probe antenna.

=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0

=C2=A0

=E2=80=9CWhat would be the radiated power of such = antenna ?=E2=80=9D

=C2=A0=

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

=C2=A0

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

=C2=A0<= /u>

=C2=A0

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 con= ductivity variations, if they monitored phase in addition to angle of arriv= al.

= =C2=A0

73,=

=C2=A0

Jim AA5BW

=C2=A0

=C2=A0

=C2=A0

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of DK7= FC
Sent: Thursday, February 1, 2018 3:27 PM
To: rsgb_lf_group@bl= acksheep.org
Subject: Re: LF: VLF Small magnetic antenna for = Tx

=C2=A0

Hi Luis,

Y= ou seem to generate much activity on all bands in your Spanish region :-) T= hat is fine!

Am 01.02.2018 19:58, schrieb VIGILANT Luis Fern=C3=A1nd= ez:

=C2=A0

As this is the =E2=80=9Cnear field=E2=80=9D it is supposed= to work only at magnetic field due to the small size of the antenna ? So o= nly 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 a= ntenna in the near field or the only chance is to be further away ?<= u>

In the moment i can receiv= e 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 wh= en using the same type of antenna as long as you are in a range of=C2=A0 &l= t; 0.7 * far field distance.


=C2=A0

Which would b= e the radiated power of such antenna ?

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

73, Stefan=


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