Return-Path: Received: from mtain-de01.r1000.mx.aol.com (mtain-de01.r1000.mx.aol.com [172.29.64.201]) by air-mf06.mail.aol.com (v129.4) with ESMTP id MAILINMF061-8bed4c656ab8380; Fri, 13 Aug 2010 11:54:32 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-de01.r1000.mx.aol.com (Internet Inbound) with ESMTP id E97FB380000E0; Fri, 13 Aug 2010 11:54:29 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OjwZC-0003h4-0d for rs_out_1@blacksheep.org; Fri, 13 Aug 2010 16:53:10 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OjwZB-0003gv-DX for rsgb_lf_group@blacksheep.org; Fri, 13 Aug 2010 16:53:09 +0100 Received: from mail-ey0-f171.google.com ([209.85.215.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OjwZ9-0001Fj-Sv for rsgb_lf_group@blacksheep.org; Fri, 13 Aug 2010 16:53:09 +0100 Received: by eyf5 with SMTP id 5so953195eyf.16 for ; Fri, 13 Aug 2010 08:53:07 -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=cEwLmk7YjytW8dY5zfTD53Vn8bQNIjWA7WbyT3NCWyo=; b=Q/Zhnu9mGNtyiCVGfR0MG/KeKT3N11w87usr7cvoqjCHEpJ/FV2iVPjWzBTdbkWxO9 wdVUaCLMG/wN1IfoB9Uljqj/PSVkPvYicwQluv/3XDOlx/cxnb2D7TacKsCa/2ZS1FiC 9IFid4xgSWiWK72diAXT3NiNS4KGlh7owEWWw= 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=lAgyvTmUJ72nYhW/9FLlHxWdycDgBXNs7oJjIija6VdcoMEc4tjdtxUVXIpQFSPOEB mDNkpeuqBtDoFvFZCPOEPX0aagk1Ama1aDJcJ76Q4SQXgyd8eBItuRf1C5q8fOXywpVr UWAnXqWeTvstL/Lh2nTSnbMZrpAzWgqyWAL1o= MIME-Version: 1.0 Received: by 10.204.176.144 with SMTP id be16mr933589bkb.53.1281714787198; Fri, 13 Aug 2010 08:53:07 -0700 (PDT) Received: by 10.204.194.69 with HTTP; Fri, 13 Aug 2010 08:53:07 -0700 (PDT) In-Reply-To: <4C6566E7.5090207@charter.net> References: <4C6566E7.5090207@charter.net> Date: Fri, 13 Aug 2010 16:53:07 +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: LF: A question about loops for 136 and 500kHz TX Content-Type: multipart/alternative; boundary=001636c5a2529827e6048db67a11 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-d303.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d40c94c656ab546d9 X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --001636c5a2529827e6048db67a11 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Wow - not bad feed back in a few minutes! Thanks everyone for chipping in with ideas and links. I guess my question was prompted by the results recently with the earth electrode antenna with the ground actually forming *part* of a loop antenn= a. The logical extension was to elevate the loop but leave the bottom running= * along* the ground (in a wire rather than relying on the soil for the retur= n path with its resistive losses). If I may pr=E9cis the responses here, you all consider this is *not* a goo= d idea and recommend elevating the lower section a few metres. I can do this= , running the lower wire along the top of the wooden garden fence (OK?) . 73s Roger G3XBM On 13 August 2010 16:38, John Andrews wrote: > Roger, > > Even in an area with very poor ground conductivity (such as mine), > environmental losses will be reduced by elevating the lower conductor.= I > would suggest 2-3 meters as a minimum. In general, loop shapes having th= e > lowest proximity to ground are the best, with circular being very desira= ble. > The late Reg Edwards, G4FGQ, wrote several programs dealing with loops= for > transmit use, and RJELOOP1 would apply the best to your situation. You= can > download it from: > http://www.we0h.us/page3.html#S301%22 > > Your actual feedpoint impedance will probably differ, but the program > allows you to play with various options in advance, perhaps saving some > money, and certainly time. > > The loop is an excellent option for a lot with so many trees that a > Marconi-style antenna would have excessive environmental losses at these > frequencies. > > John, W1TAG > > > > On 8/13/2010 11:08 AM, Roger Lapthorn wrote: > >> Having considered the antenna options for my small garden, I'm going to >> erect a TX loop antenna rather than a Marconi vertical for 136kHz: the >> earthing issues are removed and it is easier to build a capacitor >> selection box (to tune and match the loop) than wind a huge loading coi= l >> and match it. I've seen some of the webpages dealing with these and >> understand basically what is needed (large loop area, thick wire, >> capacitor match-box, dealing with high RF currents, etc). I understand >> the loop will have directionality and nulls. >> >> My question is this. *Is there any reason why the bottom of the loop >> cannot be laid along the ground rather than elevated a few metres?* Mos= t >> designs show the bottom elevated a bit, but if laid on the soil I could >> use thick coax or multiple wires for part of the loop so reducing the >> loop resistance. >> >> Views appreciated, although it may be a case of "suck it and see". >> >> 73s >> Roger G3XBM >> >> -- >> http://g3xbm-qrp.blogspot.com/ >> http://www.g3xbm.co.uk >> http://www.youtube.com/user/g3xbm >> G3XBM GQRP 1678 ISWL G11088 >> > > --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --001636c5a2529827e6048db67a11 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Wow - not bad feed back in a few minutes! Thanks everyone for chipping in= with ideas and links.

I guess my question was prompted by the resu= lts recently with the earth electrode antenna with the ground actually for= ming part of a loop antenna. The logical extension was to elevate= the loop but leave the bottom running along the ground (in a wire= rather than relying on the soil for the return path with its resistive lo= sses).

If I may pr=E9cis the responses here, you all consider this is not<= /u> a good idea and recommend elevating the lower section a few metres. I= can do this, running the lower wire along the top of the wooden garden fe= nce (OK?) .

73s
Roger G3XBM



On 13 Aug= ust 2010 16:38, John Andrews <w1tag@charter.net> wrote:
Roger,

Even in an area with very poor ground conductivity (such as mine), environ= mental losses will be reduced by elevating the lower conductor. I would su= ggest 2-3 meters as a minimum. In general, loop shapes having the lowest= proximity to ground are the best, with circular being very desirable. The= late Reg Edwards, G4FGQ, wrote several programs dealing with loops for tr= ansmit use, and RJELOOP1 would apply the best to your situation. You can= download it from:
http:/= /www.we0h.us/page3.html#S301%22

Your actual feedpoint impedance will probably differ, but the program allo= ws you to play with various options in advance, perhaps saving some money,= and certainly time.

The loop is an excellent option for a lot with so many trees that a Marcon= i-style antenna would have excessive environmental losses at these frequen= cies.

John, W1TAG



On 8/13/2010 11:08 AM, Roger Lapthorn wrote:
Having considered the antenna options for my small garden, I'm going= to
erect a TX loop antenna rather than a Marconi vertical for 136kHz: the
earthing issues are removed and it is easier to build a capacitor
selection box (to tune and match the loop) than wind a huge loading coil and match it. I've seen some of the webpages dealing with these and understand basically what is needed (large loop area, thick wire,
capacitor match-box, dealing with high RF currents, etc). I understand
the loop will have directionality and nulls.

My question is this. *Is there any reason why the bottom of the loop
cannot be laid along the ground rather than elevated a few metres?* Most designs show the bottom elevated a bit, but if laid on the soil I could use thick coax or multiple wires for part of the loop so reducing the
loop resistance.

Views appreciated, although it may be a case of "suck it and see"= ;.

73s
Roger G3XBM

--
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.u= k
http://www= .youtube.com/user/g3xbm
G3XBM =A0 GQRP 1678 =A0 =A0ISWL G11088




--
http://g3xbm-qrp.blogsp= ot.com/
http:/= /www.g3xbm.co.uk
http://www= .youtube.com/user/g3xbm
G3XBM=A0=A0 GQRP 1678=A0=A0=A0 ISWL G11088<= br> --001636c5a2529827e6048db67a11--