Return-Path: Received: from mtain-mb02.r1000.mx.aol.com (mtain-mb02.r1000.mx.aol.com [172.29.96.22]) by air-ma05.mail.aol.com (v129.4) with ESMTP id MAILINMA051-b5244bfaab682d4; Mon, 24 May 2010 12:38:00 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mb02.r1000.mx.aol.com (Internet Inbound) with ESMTP id BAFAA38000103; Mon, 24 May 2010 12:37:58 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OGadm-0002Oi-0R for rs_out_1@blacksheep.org; Mon, 24 May 2010 17:36:34 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OGadl-0002OZ-6W for rsgb_lf_group@blacksheep.org; Mon, 24 May 2010 17:36:33 +0100 Received: from mail-bw0-f43.google.com ([209.85.214.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OGadi-0008Fy-12 for rsgb_lf_group@blacksheep.org; Mon, 24 May 2010 17:36:33 +0100 Received: by bwz16 with SMTP id 16so1080337bwz.16 for ; Mon, 24 May 2010 09:36:29 -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=hyRS/ccnUn3+WaKRLZoAYV9x+/EJXGQB09pPPxQr2Tw=; b=BiIKWUmTXeuGAkB/UOAnH7Sd9EN739OhDSgqkNr2UBm5T2IBxyPK1hVQLeNvMUBpgB 3gZi2SxdQUpDNFA9f/03Zxvw+Q3/sZJmOa3iZYwcmBrjf7ZmmLIOVNZLY0o4S8aBsuhd J/ahGm4BCjqTSmGV+Nabd3U+XWTeCMLEl8ffo= 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=BHbHOoq086QQdzn33kt28IYtlxyonAVtMXwP0pZezAiSFABbnr7vR+0a3WvKmGSIPh aQAhjZGFtEzquGOujdlPD5Ybm/gAHiei5cW4U78YpSi8qJd3z8yISze+jgFCBrQtU65D m6SlE6SQjSC9i0Q+TCPJPrwCKE/Utpdk0jokQ= MIME-Version: 1.0 Received: by 10.204.140.70 with SMTP id h6mr2311753bku.1.1274718988554; Mon, 24 May 2010 09:36:28 -0700 (PDT) Received: by 10.204.58.204 with HTTP; Mon, 24 May 2010 09:36:28 -0700 (PDT) In-Reply-To: <38A51B74B884D74083D7950AD0DD85E82A1C00@File-Server-HST.hst.e-technik.tu-darmstadt.de> References: <38A51B74B884D74083D7950AD0DD85E82A1C00@File-Server-HST.hst.e-technik.tu-darmstadt.de> Date: Mon, 24 May 2010 17:36:28 +0100 Message-ID: From: Roger Lapthorn To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.9 (/) X-Spam-Report: autolearn=disabled,HTML_10_20=0.945,HTML_MESSAGE=0.001 Subject: Re: LF: AW: 8.97kHz - Near field and radiated signals? Content-Type: multipart/alternative; boundary=0015174c424e80519e048759a498 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=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: G X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m250.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d60164bfaab660601 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) --0015174c424e80519e048759a498 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Thank you for your fast reply Stefan. In answer to your questions: - Currently, my *TX electrode spacing is 10m*, which is the best I can manage in my small garden. Both electrodes are as far away from the mai= ns and other utility services as I can manage. - I have *not tried /P* transmit testing yet. - My *nearest ham who will listen/look is 3kms away*, but using beaconi= ng I am able to go out myself and see how far I can reach. This is what I= have done so far, going out into the fields behind my house with electrode= pairs or a loop receiver. Best (by ear reception) DX is 0.35kms, but the syst= em has much scope for optimisation still. - The largest single turn loop I could erect in my garden would be abou= t 50-70 sq m (about 15m top and 4m-5m high). The longest antenna length= would also be 15m horizontal with some vertical section(s) too. - The best DX targets are quite modest: I would like to exceed 1km initially with the TX power I currently have (around 4W). If I could re= ach G6ALB in the next village 3kms away I would be delighted. If I got any further I would be both amazed and VERY happy! 73s Roger G3XBM 2010/5/24 Stefan Sch=E4fer > Hello Roger, > > For your ground electrodes, ground electrodes may be the best "antenna"= in > some 10...10m. I'm not sure how to calculate field strengths but i just= know > about the 1/d^3 dependency, so twice the distance means 8 times the powe= r > for the same signal reception, in the near field. But it is the question > what are the electrodes since there is ever a coupling to the mains eart= h > and all the metallic stuff in regions where people are living so this > dependency might not be valid in your tests. As mentioned here, you coul= d > benefit from these conductors... > > But if you want to reach more distance with an antenna of the same size > (e.g. of your garden)and the same power, you could try such a TV > transformer. Take a wire, as long as possible and as high as possible,= and > apply some kV on it by this transformer. It can even be resonated by > adjusting the air gap between the both ferrite parts. That results in a > maximum output voltage and thus "ERP". At least this would be a good > alternative to your ground electrode tests. You could easily compare the > reachable distances. Here i would use a E field antenna for reception in= the > near field. > > How far is your next receiving amateur radio station away? And have you > tried to do such tests outside the village/city, just like Jim does it= with > his loop antenna? This could allow you to increase the distance of your > reception. Here, space is not limited and you could try 2x10m, 2x50m, 2x= 100m > and so on and tell us the difference in the feed point impedance at vari= ous > frequencies and your ODX :-) Maybe i will also do some ground electrode > tests in summer but i am still not sure. The complete receiver of Jim is= a > really good idea to check the QRM situation at a given QTH. Probably i= will > also buit his loop design for such tests... Would be interesing what is= the > maximum distance for a CW reception of my transmitted signal (with the= kite > antenna and 6mW ERP) ;-) > > I will also do some near field tests in this week, to compare the > performance of my 2 grabbers. This will be done here: > http://www.google.de/maps?f=3Dq&source=3Ds_q&hl=3Dde&geocode=3D&q=3Dheil= igenberg+heidelberg&sll=3D47.820666,9.312449&sspn=3D0.106733,0.219383&g=3D= heiligenberg&ie=3DUTF8&hq=3D&hnear=3DHeiligenberg&ll=3D49.419391,8.704101&= spn=3D0.001616,0.003428&t=3Dh&z=3D18in about 1,8km distance to my grabbers= . Power will also be below 100W and > the antenna wire will be mounted on a tower in abt 15m height. I will > transmit with this TV transformer on a 40m wire. > > Roger, what size is your garden? What is the maximum wire length that yo= u > can apply and in which height? What is your goal (best DX, a reals QSO= with > the next equipped station or just do some funny tests?) > > So, wish you fun and success with your experiments! > > 73, Stefan/DK7FC > > PS: What is your locator / QTH? > > --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --0015174c424e80519e048759a498 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Thank you for your fast reply Stefan.

In answer to your questions:<= br>
  • Currently, my TX electrode spacing is 10m, which is the= best I can manage in my small garden. Both electrodes are as far away fro= m the mains and other utility services as I can manage.
  • I have not tried /P transmit testing yet.
  • My nea= rest ham who will listen/look is 3kms away, but using beaconing I am= able to go out myself and see how far I can reach. This is what I have do= ne so far, going out into the fields behind my house with electrode pairs= or a loop receiver. Best (by ear reception) DX is 0.35kms, but the system= has much scope for optimisation still.
  • The largest single turn loop I could erect in my garden would be about= 50-70 sq m (about 15m top and 4m-5m high). The longest antenna length wou= ld also be 15m horizontal with some vertical section(s) too.
  • The= best DX targets are quite modest: I would like to exceed 1km initially wi= th the TX power I currently have (around 4W). If I could reach G6ALB in th= e next village 3kms away I would be delighted. If I got any further I woul= d be both amazed and VERY happy!
73s
Roger G3XBM


2010/5/= 24 Stefan Sch=E4fer <schaefer@hst.tu-darmstadt.de>
Hello Roger,

For your ground electrodes, ground electrodes may be the best "antenn= a" in some 10...10m. I'm not sure how to calculate field strength= s but i just know about the 1/d^3 dependency, so twice the distance means= 8 times the power for the same signal reception, in the near field. But= it is the question what are the electrodes since there is ever a coupling= to the mains earth and all the metallic stuff in regions where people are= living so this dependency might not be valid in your tests. As mentioned= here, you could benefit from these conductors...

But if you want to reach more distance with an antenna of the same size (e= .g. of your garden)and the same power, you could try such a TV transformer= . Take a wire, as long as possible and as high as possible, and apply some= kV on it by this transformer. It can even be resonated by adjusting the= air gap between the both ferrite parts. That results in a maximum output= voltage and thus "ERP". At least this would be a good alternati= ve to your ground electrode tests. You could easily compare the reachable= distances. Here i would use a E field antenna for reception in the near= field.

How far is your next receiving amateur radio station away? And have you tr= ied to do such tests outside the village/city, just like Jim does it with= his loop antenna? This could allow you to increase the distance of your= reception. Here, space is not limited and you could try 2x10m, 2x50m, 2x1= 00m and so on and tell us the difference in the feed point impedance at va= rious frequencies and your ODX :-) Maybe i will also do some ground electr= ode tests in summer but i am still not sure. The complete receiver of Jim= is a really good idea to check the QRM situation at a given QTH. Probably= i will also buit his loop design for such tests... Would be interesing wh= at is the maximum distance for a CW reception of my transmitted signal (wi= th the kite antenna and 6mW ERP) ;-)

I will also do some near field tests in this week, to compare the performa= nce of my 2 grabbers. This will be done here: http://www.google.de/maps?f=3Dq&source=3Ds_q&hl= =3Dde&geocode=3D&q=3Dheiligenberg+heidelberg&sll=3D47.820666,9= .312449&sspn=3D0.106733,0.219383&g=3Dheiligenberg&ie=3DUTF8&am= p;hq=3D&hnear=3DHeiligenberg&ll=3D49.419391,8.704101&spn=3D0.0= 01616,0.003428&t=3Dh&z=3D18 in about 1,8km distance to my grab= bers. Power will also be below 100W and the antenna wire will be mounted= on a tower in abt 15m height. I will transmit with this TV transformer on= a 40m wire.

Roger, what size is your garden? What is the maximum wire length that you= can apply and in which height? What is your goal (best DX, a reals QSO wi= th the next equipped station or just do some funny tests?)

So, wish you fun and success with your experiments!

73, Stefan/DK7FC

PS: What is your locator / QTH?




--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G11088
--0015174c424e80519e048759a498--