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 w6GELpYV001999 for ; Mon, 16 Jul 2018 16:21:54 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ff4Ir-0007yu-Bo for rs_out_1@blacksheep.org; Mon, 16 Jul 2018 15:16:41 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ff4Iq-0007yl-EY for rsgb_lf_group@blacksheep.org; Mon, 16 Jul 2018 15:16:40 +0100 Received: from lb2-smtp-cloud7.xs4all.net ([194.109.24.28]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1ff4Io-0006v4-Rk for rsgb_lf_group@blacksheep.org; Mon, 16 Jul 2018 15:16:39 +0100 Received: from [192.168.178.20] ([83.162.220.82]) by smtp-cloud7.xs4all.net with ESMTP id f4ImfP5ZR6brUf4InfObJM; Mon, 16 Jul 2018 16:16:38 +0200 From: "Roelof Bakker" To: N1BUG , rsgb_lf_group@blacksheep.org Date: Mon, 16 Jul 2018 16:16:35 +0200 MIME-Version: 1.0 Message-ID: <5B4CA8C3.30032.1B0A9C7@roelof.ndb.demon.nl> In-reply-to: <19bdcc7f-1f73-8660-420a-0858bd24beaf@n1bug.com> References: , <5B4C78A7.1010208@posteo.de>, <19bdcc7f-1f73-8660-420a-0858bd24beaf@n1bug.com> X-mailer: Pegasus Mail for Windows (4.72.572) Content-description: Mail message body X-CMAE-Envelope: MS4wfEwqBdPiBdshevoOzOOyERfw6NuFI0sqhWo5h1zP3PE3A069GRgYRCXThkPUnnV4bRSsIxenpumnpCw/cGXrgi+qH19FvbtRVKEfUq19v8+qye388w7W 6BScnDZLkXpp3ng/XQfS0xNiBYg95vfpJjKHk0mqaNpbfeSEF887/oX/2QQbOVg8KiX4GjM2UQ52gkj3YFNuipET5yH3la5uriVf3EGaWKfs6X2zi0aHa7Em X-Spam-Score: -0.7 (/) 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 @@CONTACT_ADDRESS@@ for details. Content preview: Hello Paul, Noise received on your TX antenna is re-transmitted and this is responsible for the increase in noise level on your RX antenna. One way to get rid of it is to detune your TX antenna on receive. [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [194.109.24.28 listed in list.dnswl.org] X-Scan-Signature: bb61bee384896e075004ae5ec954ddd2 Subject: Re: LF: TX > RX isolation test Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT 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=none 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 Hello Paul, Noise received on your TX antenna is re-transmitted and this is responsible for the increase in noise level on your RX antenna. One way to get rid of it is to detune your TX antenna on receive. I have been using an active E-probe antenna since 2004 with very rewarding results on LF / MF, albeit mounted just 6 meter from my house. The band noise from the antenna at 477 kHz is 14 dB over the noise floor of my PERSEUS, so sensitivity is more than needed. There is no need for a good radio earth with this type of antenna, due to the small capacitances involved, typical 3 pF. This antenna is prone to common mode problems. I have solved this by connecting the shield of the coax to a ground stake at the bottom of the mast and near the house. Requirements for this ground are modest. On poor soil one square metre of chicken wire will work already. A suitable common mode choke, e.g. 20 turns RG174 on a FT-140-77 toroid can help as well. To achieve best results some experimentation is on order, which is time well spent! 73, Roelof Bakker, pa0rdt