Return-Path: Received: from mtain-da05.r1000.mx.aol.com (mtain-da05.r1000.mx.aol.com [172.29.64.77]) by air-ma04.mail.aol.com (v129.4) with ESMTP id MAILINMA043-b5194c095904395; Fri, 04 Jun 2010 15:50:28 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-da05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 38C88380000D3; Fri, 4 Jun 2010 15:50:27 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OKcsu-0005xf-3E for rs_out_1@blacksheep.org; Fri, 04 Jun 2010 20:48:52 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OKcst-0005xW-CD for rsgb_lf_group@blacksheep.org; Fri, 04 Jun 2010 20:48:51 +0100 Received: from mail-bw0-f43.google.com ([209.85.214.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OKcsq-0005bJ-6g for rsgb_lf_group@blacksheep.org; Fri, 04 Jun 2010 20:48:51 +0100 Received: by bwz3 with SMTP id 3so468009bwz.16 for ; Fri, 04 Jun 2010 12:48:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=pupbHIV3KcL7MvTQxowbAjb0E8rGi+/vK9mBZmaYgKY=; b=NQZMHpTlF4bNl1tIPulyavzO2sRSK6qxqBYJyw4ezYG1tY3KuiPFtSc2mHeT0/2xc9 LshVJUeHRq08tRmjMhJM9WvHll4R42zG0r5NkB4zjnffRamgIBWEyaR++Detz/YcQHNq Wvj2DWD7ZN96Ox/fQP2eyKgOi+FhTTpfNyQW0= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=am/VebDBZbE4KzLB2pMgkih/vcszFQJtsu9vWcukxw149voDMwyCxqnloz16bB85Gu vb6rRvxoTUaGz6NwaIhfxYZRC3cZLDtLiF6uF13Azi/56xRN7WANK7bV6kfahesTTpMx WIvUWd2yWjxg18dPIi4BvodY5n8zYwzWwlcHA= MIME-Version: 1.0 Received: by 10.204.140.153 with SMTP id i25mr4355667bku.169.1275680926559; Fri, 04 Jun 2010 12:48:46 -0700 (PDT) Received: by 10.204.58.204 with HTTP; Fri, 4 Jun 2010 12:48:46 -0700 (PDT) In-Reply-To: <4C09114F.5090605@iup.uni-heidelberg.de> References: <001401cb02f4$4aa9d130$0401a8c0@xphd97xgq27nyf> <00b701cb030b$c6268d50$0201a8c0@Clemens04> <01CA4D0605FB409ABD7D2F0A98DC46BD@df2py> <4C08002C.5070500@iup.uni-heidelberg.de> <4C09114F.5090605@iup.uni-heidelberg.de> Date: Fri, 4 Jun 2010 20:48:46 +0100 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: VLF: 2km on 8,97 kHz using 6W TX power and a 120m earth antenna Content-Type: multipart/alternative; boundary=0015174789dc796d420488399ca7 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=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: S X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m271.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d404d4c0959036559 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --0015174789dc796d420488399ca7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Stefan, A few observations on your tests using the earth electrode "antenna" today= : 1. In my experience, most of the signal transmission is by induction,= so I think it would be worth trying to receive the signal with a loop ante= nna when the received signal may be much stronger than on the E-field probe= . In my case I use a 30turn, 80cm square, loop which can be rotated to minim= ise 50Hz interference. 2. On my 10m and 20m baseline earth electrodes I was measuring resistan= ce of between 40-60 ohms between 1-9kHz, so your figure seems very high.= This may be as a result of the soil and rock type in your area but this is= worth checking. If my theory of the "loop in the ground" is correct then a po= or conductivity soil would result in a larger effective loop area within= the ground. 3. Did you try matching the PA to this high impedance through a transformer? I think not in this test, so better results may well be possible. 4. Regarding Mal's comment about "you need a 100m high antenna", well= you know this works, but the point of this experiment is to see how effecti= ve, or not, an electrode "antenna" is. The results are valuable whether goo= d or not. Here, I have completed a further "by ear" range test using my TDA2003 4W= PA into a 20m base electrode pair "antenna" walking around the village in man= y different directions using the 80cm loop RX at around 1.5kHz. I improved= the 50Hz rejection this week by adding another Sallen-Key HPF. When walking ov= er metal pipework in the roads the signal is strong up to at least 0.25km in almost any direction and limited by 50Hz noise. When walking across fields well away from pipework the loop orientation exactly lines up with the bas= e electrode "loop in the ground" at distances up to 0.5km. I have not manag= ed to hear the signal at any further distance in any direction. My grandson= is back staying with us all next week, so very limited chance for more experiments until about June 14th. I have a long list of things to try still! 73s Roger G3XBM 2010/6/4 Stefan Sch=E4fer > Dear VLF, > > As mentioned in the subject i have done a test on 8,97 kHz today in the > morning, where the natural QRN has it's lowest level during the day. > > I used a 120m long wire antenna that was placed just on the ground. Sinc= e > the earth losses were very high i have jut got 6W TX power out of my 300= W > PA. > > See my detailed report with many pictures and the results on: > http://www.iup.uni-heidelberg.de/schaefer_vlf/Earth_antenna_120m_transmi= ssion_2km_DK7FC.pdf > > > Today, there were transmissions at least by DJ2LF, DF6NM, DK7FC on the > dreamers band. It seems we need something like a band plan soon, hi :-) > > Best 73 and good luck, Dreamers! > > 73, Stefan/DK7FC > --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --0015174789dc796d420488399ca7 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Stefan,

A few observations on your tests using the earth electrode= "antenna" today:
  1. In my experience, most of the signa= l transmission is by induction, so I think it would be worth trying to rec= eive the signal with a loop antenna when the received signal may be much= stronger than on the E-field probe. In my case I use a 30turn, 80cm squar= e, loop which can be rotated to minimise 50Hz interference.
  2. On my 10m and 20m baseline earth electrodes I was measuring resis= tance of between 40-60 ohms between 1-9kHz, so your figure seems very high= . This may be as a result of the soil and rock type in your area but this= is worth checking. If my theory of the "loop in the ground" is= correct then a poor conductivity soil would result in a larger effective= loop area within the ground.
  3. Did you try matching the PA to this high impedance through a tran= sformer? I think not in this test, so better results may well be possible.=
  4. Regarding Mal's comment about "you need a 100m high ante= nna", well you know this works, but the point of this experiment is= to see how effective, or not, an electrode "antenna" is. The re= sults are valuable whether good or not.
Here, I have completed a further "by ear" range test= using my TDA2003 4W PA into a 20m base electrode pair "antenna"= walking around the village in many different directions using the 80cm lo= op RX at around 1.5kHz. I improved the 50Hz rejection this week by adding= another Sallen-Key HPF. When walking over metal pipework in the roads the= signal is strong up to at least 0.25km in almost any direction and limite= d by 50Hz noise. When walking across fields well away from pipework the lo= op orientation exactly lines up with the base electrode "loop in the= ground" at distances up to 0.5km.=A0 I have not managed to hear the= signal at any further distance in any direction. My grandson is back stay= ing with us all next week, so very limited chance for more experiments unt= il about June 14th. I have a long list of things to try still!

73s
Roger G3XBM



2010/6/4= Stefan Sch=E4fer <Stefan.Schaefer@iup.uni-heidelberg.de>
=20
Dear VLF,

As mentioned in the subject i have done a test on 8,97 kHz today in the morning, where the natural QRN has it's lowest level during the day.
I used a 120m long wire antenna that was placed just on the ground. Since the earth losses were very high i have jut got 6W TX power out of my 300W PA.

See my detailed report with many pictures and the results on: http://www.iup.uni-heidelb= erg.de/schaefer_vlf/Earth_antenna_120m_transmission_2km_DK7FC.pdf


Today, there were transmissions at least by DJ2LF, DF6NM, DK7FC on the dreamers band. It seems we need something like a band plan soon, hi :-)
Best 73 and good luck, Dreamers!

73, Stefan/DK7FC



--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088
--0015174789dc796d420488399ca7--