Return-Path: Received: from mtain-df11.r1000.mx.aol.com (mtain-df11.r1000.mx.aol.com [172.29.64.223]) by air-me03.mail.aol.com (v129.4) with ESMTP id MAILINME034-8bab4ca0f37d279; Mon, 27 Sep 2010 15:41:49 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-df11.r1000.mx.aol.com (Internet Inbound) with ESMTP id 1D52838000145; Mon, 27 Sep 2010 15:41:47 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1P0JYN-0005FB-2m for rs_out_1@blacksheep.org; Mon, 27 Sep 2010 20:39:59 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1P0JYC-0005Ey-Jt for rsgb_lf_group@blacksheep.org; Mon, 27 Sep 2010 20:39:48 +0100 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1P0JYA-00063F-Ra for rsgb_lf_group@blacksheep.org; Mon, 27 Sep 2010 20:39:50 +0100 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 476477B8077 for ; Mon, 27 Sep 2010 21:39:38 +0200 (CEST) Received: from ICTS-S-HUB-N4.luna.kuleuven.be (icts-s-hub-n4.luna.kuleuven.be [10.112.9.14]) by smtps01.kuleuven.be (Postfix) with ESMTP id 1A08A31E703 for ; Mon, 27 Sep 2010 21:39:38 +0200 (CEST) Received: from ICTS-S-EXC2-CA.luna.kuleuven.be ([10.112.11.13]) by ICTS-S-HUB-N4.luna.kuleuven.be ([10.112.9.14]) with mapi; Mon, 27 Sep 2010 21:39:38 +0200 X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe To: "rsgb_lf_group@blacksheep.org" Date: Mon, 27 Sep 2010 21:39:38 +0200 Thread-Topic: Loops on TX Thread-Index: ActeaZdP/quVBcdgTeOYLnPQJblETgAEWa51 Message-ID: References: In-Reply-To: Accept-Language: nl-NL, nl-BE Content-Language: nl-BE X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: nl-NL, nl-BE MIME-Version: 1.0 X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: RE: Loops on TX Content-Type: multipart/alternative; boundary="_000_BF4A524700075746A6467658DFC7102C886E0FF444ICTSSEXC2CAlu_" 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_20_30,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 x-aol-global-disposition: S X-AOL-REROUTE: YES x-aol-sid: 3039ac1d40df4ca0f37a7e3a X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --_000_BF4A524700075746A6467658DFC7102C886E0FF444ICTSSEXC2CAlu_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Roger, the AC current through the loop wire will induce a (loss) current in any= other conductor near it. This includes ground, wet wood etc... The larger= the distance to other conductors the less the induced current (and thus= the loss). Although a loop antenna is far less degraded by lossy object near it comp= ared to a vertical antenna, these losses cannot be neglected. The loop you have now has already a large loss resistance due to the thin= (1mm) wire, so other losses will be masked. Maybe for that reason you hav= e not noticed any difference by placing the bottom wire on the ground. 73, Rik ON7YD - OR7T ________________________________ Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or= g] namens Roger Lapthorn [rogerlapthorn@gmail.com] Verzonden: maandag 27 september 2010 19:24 Aan: rsgb_lf_group@blacksheep.org Onderwerp: LF: Loops on TX Good to see the reflector back again. For the last week or so I've been running my vertical "fully in the air"= TX loop (1mm diameter wire, 80m sq area) on both 137 and 500kHz. Now, the= bottom of the loop is laying right on the lawn with no attempt to raise= it off the ground. Weather has been mixed and yesterday it rained all day= . Results on 500kHz suggest it is every bit as good (actually better) than= my top loaded Marconi used last winter with best DX so far with 2mW ERP= being LA3EQ last evening (heavy rain all day and evening). Results on 136= kHz with <20uW ERP have been encouraging too with 6 different WSPR reports= out to 148km. I clearly know that improving the wire diameter will improv= e the ERP simply as a result of reducing resistive losses. What I'm less= clear about is why people say all of the loop should be raised above the= ground. My questions are these: * What additional losses, if any, do I suffer having the loop on the gr= ound (even wet ground)? How do these arise? * Could I bury the return part of the loop wire in the ground and maybe= gain a few more square metres of area? * Is there anywhere where I can get a simple explanation of loop losses= due to ground presence and foliage presence? In the last year a lot of accepted theory/beliefs, for example on earth el= ectrode antennas, has proved to be questionable and I am wondering if the= "loop must be in the air and away from foliage" is another accepted "fact= " which needs to be questioned. 73s Roger G3XBM -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm G3XBM GQRP 1678 ISWL G11088 --_000_BF4A524700075746A6467658DFC7102C886E0FF444ICTSSEXC2CAlu_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Roger,
 
the AC current through the loop wire= will induce a (loss) current in any other conductor near it. This include= s ground, wet wood etc... The larg= er the distance to other conductors the less the induced current (and thus the loss).
Althou= gh a loop antenna  is far less degraded by lossy object near it compa= red to a vertical antenna, these losses cannot be neglected.
The loop you have now ha= s already a large loss resistance due to the thin (1mm) wire, so other los= ses will be masked. Maybe for that reason you have not noticed any differe= nce by placing the bottom wire on the ground.
 
73, Rik  ON7YD - OR= 7T
 
Van: owner-rsgb_= lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Roger= Lapthorn [rogerlapthorn@gmail.com]
Verzonden: maandag 27 september 2010 19:24
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF: Loops on TX

Good to see the reflector back again.

For the last week or so I've been running my vertical "fully in the= air" TX loop (1mm diameter wire, 80m sq area) on both 137 and 500kHz= . Now, the bottom of the loop is laying right on the lawn with no attempt= to raise it off the ground. Weather has been mixed and yesterday it rained all day. Results on 500kHz suggest it is every bi= t as good (actually better) than my top loaded Marconi used last winter wi= th best DX so far with 2mW ERP being LA3EQ last evening (heavy rain all da= y and evening). Results on 136kHz with <20uW ERP have been encouraging too with 6 different WSPR reports out= to 148km. I clearly know that improving the wire diameter will improve th= e ERP simply as a result of reducing resistive losses. What I'm less clear= about is why people say all of the loop should be raised above the ground.

My questions are these:
  • What additional losses, if any, do I suffer having the loop on the gro= und (even wet ground)? How do these arise?
  • Could I bury the return part of the loop wire in the ground and= maybe gain a few more square metres of area?
  • Is there anywhere where I can get a simple explanation of loop lo= sses due to ground presence and foliage presence?
In the last year a lot of accepted theory/beliefs, for example on earth el= ectrode antennas, has proved to be questionable and I am wondering if the= "loop must be in the air and away from foliage" is another acce= pted "fact" which needs to be questioned.

73s
Roger G3XBM

--
http://g3xbm-= qrp.blogspot.com/
http://www.g3xbm.co.u= k
http://www= .youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088
--_000_BF4A524700075746A6467658DFC7102C886E0FF444ICTSSEXC2CAlu_--