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 w11Jbgd8032122 for ; Thu, 1 Feb 2018 20:37:45 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ehKZi-0005he-Lh for rs_out_1@blacksheep.org; Thu, 01 Feb 2018 19:31:10 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ehKZb-0005hV-Hm for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 19:31:03 +0000 Received: from mail-wr0-x233.google.com ([2a00:1450:400c:c0c::233]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1ehKZY-0007nW-7r for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 19:31:02 +0000 Received: by mail-wr0-x233.google.com with SMTP id i56so20228938wra.7 for ; Thu, 01 Feb 2018 11:30:59 -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=from:message-id:mime-version:subject:date:in-reply-to:cc:to :references; bh=Sm9akpeAJVYBKCDdDCwbRuTfhx2X6Mw2XNaT4SuaW6Y=; b=jodQLVkLtPcCXencvKR9WzBPinDYGkOnlNwEhJMe1xz95ZCsl+u/SzoO9scBwg5TKI Qq4PG1EyGCDtTfmlnKKkDRuCW1v8GEArewDE5MHATy91juhFy9pFjwVvE8Ycv60szt3i BJGUavo2fFH5DeQEiXvreRofZXRQ4KTXdB2KTmhhh8qxfgY8gwvd6GpqdR08VxP/+qG1 5WNRQSUSHQDnz0MGxgymZsSPqfnT1VswSR4fvsGUT8xNcb3rkIKMPMwbi6obdZ5LghC8 491WuOi28Qyg22tLFCTb73MqbsI4nxz/f4AW83bTlMSROV8xp3zjOqRWBNwS8LwY31JN +yHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:message-id:mime-version:subject:date :in-reply-to:cc:to:references; bh=Sm9akpeAJVYBKCDdDCwbRuTfhx2X6Mw2XNaT4SuaW6Y=; b=J+DLtLoUOQqn+Dy4k2/TGxDv/cCy2nFN/1+iJtnIpjeA2dFsXqs9Uk+u7DA4AgRlBx QlWEeiD2xzvckbsl0m59E5U0vDvP+kAk1XzawYCSG50s5r+MG7a9dHYYTKMxjEDdr+ZM orWuIXJ7UMyrfgJpQUvsFAbHHCzRAljTs85l4f6cGMMqWzlJZBt+6+Q7Z4zTZbc5zx2G 874mqlhx9WP673qHhE+cHJj5/Dfq0T3wtNr3BwfhPJVdXQsmFq0PX12IcDK27yYQyqIJ oqeddEs+gFWdAHgadrc79+HnNpYSetFIe/4z/OMooGqTSRav7uZMk2spifUmBjzrd3cZ L7vA== X-Gm-Message-State: AKwxytdzFhihFvZ285JbFQ1HpLNOq91HUmGZ+pjC6Ge3IvIFC19gqE8Y F77RnXlW+qmLQJGlmlf8TISc5b+E X-Google-Smtp-Source: AH8x227zIG/PVjkwXrHQnQ/WIvDkZ8yS/hcyRvpfCHf4Wuu8AolSMPU83UULwG4ACk+2SogarCWLsg== X-Received: by 10.223.179.209 with SMTP id x17mr3394389wrd.162.1517513459086; Thu, 01 Feb 2018 11:30:59 -0800 (PST) Received: from [127.0.0.1] ([82.98.23.94]) by smtp.gmail.com with ESMTPSA id w133sm836978wmg.5.2018.02.01.11.30.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Feb 2018 11:30:58 -0800 (PST) From: John Rabson Message-Id: Mime-Version: 1.0 (Mac OS X Mail 11.2 \(3445.5.20\)) Date: Thu, 1 Feb 2018 20:30:45 +0100 In-Reply-To: <579355A36AEE9D4FA555C45D556003AB9AB485D3@servigilant.vigilant.local> Cc: =?utf-8?Q?VIGILANT_Luis_Fern=C3=A1ndez?= , Rob Gill , Mike Bedford To: rsgb_lf_group@blacksheep.org References: <579355A36AEE9D4FA555C45D556003AB9AB485D3@servigilant.vigilant.local> X-Mailer: Apple Mail (2.3445.5.20) X-Spam-Score: 0.3 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. 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Content preview: Luis, I think this system would be of interest to other caving groups, so I am copying your posting to the editors of the Cave Radio & Electronics Journal in the UK. 73 John F5VLF [...] Content analysis details: (0.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.2 FREEMAIL_ENVFROM_END_DIGIT Envelope-from freemail username ends in digit (john.rabson07[at]gmail.com) 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (john.rabson07[at]gmail.com) 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: b99b9f5ebb2905dfac0746d3f825052c Content-Type: multipart/alternative; boundary="Apple-Mail=_52451D12-0E4F-4A73-BFF1-C4AD8228F616" Subject: Re: LF: VLF Small magnetic antenna for Tx 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=FROM_ENDS_IN_NUMS,HTML_50_60, 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 --Apple-Mail=_52451D12-0E4F-4A73-BFF1-C4AD8228F616 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 Luis, I think this system would be of interest to other caving groups, so I am = copying your posting to the editors of the Cave Radio & Electronics = Journal in the UK. 73 John F5VLF > On 1 Feb 2018, at 19:58, VIGILANT Luis Fern=C3=A1ndez = wrote: >=20 > Hi VLF > =20 > I=E2=80=99m in contact with a local group of espeleo enthusiast, big = enought to count with some electronic tecnicians with them > They have been developing their own equipment at VLF. A transmitter = which is carried down the cavity and turned on Tx > Directional receivers using ferrite antennas are used at surface to = determine the angles to the transmitter, so to accurately > track a number of sites in the cavity and get a map of it > =20 > The transmitter has been even used to send CW connecting by Bluettoth = with a rugerized Android phone running a CW keying App > Inverse process at surface provided decode of the CW messages (clear = aural copy but not CW OMs in the group) > Not EbNaut planned so far ;-) > =20 > Talking with Juan Leandro, who is making most of the design and tests = in this equipments, we had a discussion about which > would be the performance of such antenna in open field as VHF = transmitter. Obviously we have not tested it yet with my Rx > but it is on schedule. In the meantime I think would be interesting to = discuss this in the reflector > =20 > The antenna is made by using two ferrite cores from CRT deflection = coils with 100 turns of 2.3mm copper wire, which provide > 1740 uH. Then a battery of caps providing 9.9nF resonate the antenna = at 38400 Hz. For the PA and rest of the circuit you can see > the schematic in this link = https://www.dropbox.com/s/6onj8atfo24v5ko/Summer%201esq.pdf?dl=3D0 = > =20 > So far the tests conducted in cavity worked very good at 70m trought = the rocks. But taking it =E2=80=9Cout=E2=80=9D for test rises some = questions: > =20 > 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 only = magnetic field for > underground signals at this distances ? > =20 > 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 ? > And then loosing the signal due to the distance =E2=80=A6. > =20 > Which would be the radiated power of such antenna ? (may be I would = have to ask Juan Leandro for more details about currents) > =20 > =20 > 73 de Luis > EA5DOM --Apple-Mail=_52451D12-0E4F-4A73-BFF1-C4AD8228F616 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8 Luis,

I = think this system would be of interest to other caving groups, so I am = copying your posting to the editors of the Cave Radio & = Electronics Journal in the UK.

73 John F5VLF

On 1 Feb = 2018, at 19:58, VIGILANT Luis Fern=C3=A1ndez <luis@vigilant.es> = wrote:

Hi VLF
 
I=E2=80=99m in contact with a = local group of espeleo enthusiast, big enought to count with some = electronic tecnicians with them
They = have been developing their own equipment at VLF. A transmitter which is = carried down the cavity and turned on Tx
Directional receivers using ferrite antennas = are used at surface to determine the angles to the transmitter, so to = accurately
track a number of sites in = the cavity and get a map of it
 
The transmitter has been even = used to send CW connecting by Bluettoth with a rugerized Android phone = running a CW keying App
Inverse = process at surface provided decode of the CW messages (clear aural copy = but not CW OMs in the group)
Not = EbNaut planned so far ;-)
 
Talking with Juan Leandro, = who is making most of the design and tests in this equipments, we had a = discussion about which
would = be the performance of such antenna in open field as VHF transmitter. = Obviously we have not tested it yet with my Rx
but it is on schedule. In the meantime I think = would be interesting to discuss this in the reflector
 
The = antenna is made by using two ferrite cores from CRT deflection coils = with 100 turns of 2.3mm copper wire, which provide
1740 uH. Then a battery of caps providing = 9.9nF resonate the antenna at 38400 Hz. For the PA and rest of the = circuit you can see
the = schematic in this link https://www.dropbox.com/s/6onj8atfo24v5ko/Summer%201esq.pdf?dl=3D= 0
 
So far the tests conducted in = cavity worked very good at 70m trought the rocks. But taking it = =E2=80=9Cout=E2=80=9D for test rises some questions:
 
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 only magnetic = field for
underground signals at this = distances ?
 
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 ?
And = then loosing the signal due to the distance =E2=80=A6.
 
Which = would be the radiated power of such antenna ?  (may be I would have = to ask Juan Leandro for more details about currents)
 
 
73 de Luis
EA5DOM

= --Apple-Mail=_52451D12-0E4F-4A73-BFF1-C4AD8228F616--