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 w6JGvleR009890 for ; Thu, 19 Jul 2018 18:57:49 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fgCA7-0007m0-7B for rs_out_1@blacksheep.org; Thu, 19 Jul 2018 17:52:19 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fgC9V-0007lp-5x for rsgb_lf_group@blacksheep.org; Thu, 19 Jul 2018 17:51:41 +0100 Received: from lb1-smtp-cloud9.xs4all.net ([194.109.24.22]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1fgC9T-0006Aw-3q for rsgb_lf_group@blacksheep.org; Thu, 19 Jul 2018 17:51:39 +0100 Received: from [192.168.178.20] ([83.162.220.82]) by smtp-cloud9.xs4all.net with ESMTP id gC9QfD7EtEJtcgC9Rf4uDp; Thu, 19 Jul 2018 18:51:37 +0200 From: "Roelof Bakker" To: rsgb_lf_group@blacksheep.org Date: Thu, 19 Jul 2018 18:51:36 +0200 MIME-Version: 1.0 Message-ID: <5B50C198.9179.22CB3AF@roelof.ndb.demon.nl> In-reply-to: References: , <5B5043E7.7020302@posteo.de>, X-mailer: Pegasus Mail for Windows (4.72.572) Content-description: Mail message body X-CMAE-Envelope: MS4wfDttoumFQ6E3h0XZFnES9xWyqWg1zIS/AO+Eji/wR3HOlxg3BAxjekH+BrTYNSM6d77WvMeBLVeZmKdV5OVCI9cHgOYMs5ZbF2PIUjTq9S88CCYJm2u/ IZfT3zcE0Y93cS/BkJF0A13vKpv1/m3pmQerS3/ELCrc4qGHGOmcAcagmT3iGEciM0vZjHtnKaq5Sg== 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, There is no need to mount a mini-whip very high. 5 meter is about optimum. Higher will give stronger signals and noise, so nothing is gained. Don't worry about the screening effect of trees on receive. What happens is that there will be some attenuation, but the band noise is attenuated by the same amount as the signal, so signal to noise ratio is not impaired. These antennas provide ample signal levels and at LF there is a lot of leeway. [...] 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 [194.109.24.22 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H3 RBL: Good reputation (+3) [194.109.24.22 listed in wl.mailspike.net] -0.0 RCVD_IN_MSPIKE_WL Mailspike good senders X-Scan-Signature: 0a4643e586472c13187d293ec5d096c2 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, There is no need to mount a mini-whip very high. 5 meter is about optimum. Higher will give stronger signals and noise, so nothing is gained. Don't worry about the screening effect of trees on receive. What happens is that there will be some attenuation, but the band noise is attenuated by the same amount as the signal, so signal to noise ratio is not impaired. These antennas provide ample signal levels and at LF there is a lot of leeway. My mini-whip is mounted in a hawthorn tree and there are a couple of large chestnut trees nearby. At 400 kHz, the difference between dry and wet foliage is only 2 dB, which is no problem. There is no need to use an actual whip. Stefan suggest a whip of 0.3 meter. I have tested this and found that a PCB-antenna of 30 x 40 mm produces the same signal level. Besides a smaller size, which is not important of course, it will be less susceptible to lightning damage. The same applies for a K9AY. There is no need to scale it for 137 kHz. The directive properties are not effected by size, only the output will suffer. You might mount it on your 9 meter LNV and see how it works. 73, Roelof, pa0rdt