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 w11J54f5032060 for ; Thu, 1 Feb 2018 20:05:06 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ehK4D-0005V1-00 for rs_out_1@blacksheep.org; Thu, 01 Feb 2018 18:58:37 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ehK4B-0005Us-8Z for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 18:58:35 +0000 Received: from gmy2-mh808.smtproutes.com ([94.186.192.137]) by relay1.thorcom.net with esmtp (Exim 4.89) (envelope-from ) id 1ehK47-0007fM-VV for rsgb_lf_group@blacksheep.org; Thu, 01 Feb 2018 18:58:34 +0000 X-Katharion-ID: 1517511493.38081.gmy2-mh808 Received: from servigilant.vigilant.es ([85.60.35.36]) by gmy2-mh808.smtproutes.com [(94.186.192.137)] with ESMTP via TCP (TLSv1/TLS_DHE_RSA_WITH_AES_256_CBC_SHA); 01 Feb 2018 18:58:13 +0000 Received: from servigilant.vigilant.local ([fe80::c40d:8140:d722:5448]) by servigilant.vigilant.local ([fe80::c40d:8140:d722:5448%13]) with mapi id 14.03.0123.003; Thu, 1 Feb 2018 19:58:11 +0100 From: =?iso-8859-1?Q?VIGILANT_Luis_Fern=E1ndez?= To: "rsgb_lf_group@blacksheep.org" Thread-Topic: VLF Small magnetic antenna for Tx Thread-Index: AdObiQyh63VNGvw4QcWtV8Wk8Q5/tQ== Date: Thu, 1 Feb 2018 18:58:10 +0000 Message-ID: <579355A36AEE9D4FA555C45D556003AB9AB485D3@servigilant.vigilant.local> Accept-Language: es-ES, en-US Content-Language: es-ES X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [192.168.0.18] MIME-Version: 1.0 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: Hi VLF I'm 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 [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: 7c995d39cde70605aa76dd18810a4256 Subject: LF: VLF Small magnetic antenna for Tx Content-Type: multipart/alternative; boundary="_000_579355A36AEE9D4FA555C45D556003AB9AB485D3servigilantvigi_" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_40_50,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 --_000_579355A36AEE9D4FA555C45D556003AB9AB485D3servigilantvigi_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi VLF I'm in contact with a local group of espeleo enthusiast, big enought to cou= nt with some electronic tecnicians with them They have been developing their own equipment at VLF. A transmitter which i= s carried down the cavity and turned on Tx Directional receivers using ferrite antennas are used at surface to determi= ne 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 th= is 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 disc= uss this in the reflector The antenna is made by using two ferrite cores from CRT deflection coils wi= th 100 turns of 2.3mm copper wire, which provide 1740 uH. Then a battery of caps providing 9.9nF resonate the antenna at 384= 00 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 So far the tests conducted in cavity worked very good at 70m trought the ro= cks. But taking it "out" for test rises some questions: As this is the "near field" it is supposed to work only at magnetic field d= ue 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 n= ear field or the only chance is to be further away ? And then loosing the signal due to the distance .... Which would be the radiated power of such antenna ? (may be I would have t= o ask Juan Leandro for more details about currents) 73 de Luis EA5DOM --_000_579355A36AEE9D4FA555C45D556003AB9AB485D3servigilantvigi_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Hi VLF

 

I’m in contact with a loc= al group of espeleo enthusiast, big enought to count with some electronic t= ecnicians with them

They have been developing their= own equipment at VLF. A transmitter which is carried down the cavity and t= urned on Tx

Directional receivers using fer= rite antennas are used at surface to determine the angles to the transmitte= r, so to accurately

track a number of sites in the = cavity and get a map of it

 

The transmitter has been even u= sed to send CW connecting by Bluettoth with a rugerized Android phone runni= ng a CW keying App

Inverse process at surface prov= ided decode of the CW messages (clear aural copy but not CW OMs in the grou= p)

Not EbNaut planned so far ;-)

 

Talking with Juan Leandro, who = is making most of the design and tests in this equipments, we had a discuss= ion about which

would be the performance of suc= h antenna in open field as VHF transmitter. Obviously we have not tested it= yet with my Rx

but it is on schedule. In the m= eantime I think would be interesting to discuss this in the reflector<= /o:p>

 

The antenna is made by using tw= o ferrite cores from CRT deflection coils with 100 turns of 2.3mm copper wi= re, which provide

1740 uH. Then a battery of caps= providing 9.9nF resonate the antenna at 38400 Hz. For the PA and rest of t= he circuit you can see

the schematic in this link https://www.dropbox.com/s/6onj8atfo24v5ko/Summer%201esq.pdf?dl=3D0=

 

So far the tests conducted in c= avity worked very good at 70m trought the rocks. But taking it “out&#= 8221; for test rises some questions:

 

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

underground signals at this dis= tances ?

 

Can we expect to receive the si= gnal 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 ….

 

Which would be the radiated pow= er of such antenna ?  (may be I would have to ask Juan Leandro for mor= e details about currents)

 

 

73 de Luis

EA5DOM

 

 

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