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[195.171.43.25]) by mx.google.com with ESMTP id wg1si1982597wjb.115.2014.03.03.14.08.31 for ; Mon, 03 Mar 2014 14:08:32 -0800 (PST) Received-SPF: neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) client-ip=195.171.43.25; Authentication-Results: mx.google.com; spf=neutral (google.com: 195.171.43.25 is neither permitted nor denied by best guess record for domain of owner-rsgb_lf_group@blacksheep.org) smtp.mail=owner-rsgb_lf_group@blacksheep.org Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1WKZVf-0002c8-Fb for rs_out_1@blacksheep.org; Mon, 03 Mar 2014 20:30:47 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1WKZVe-0002bz-Hg for rsgb_lf_group@blacksheep.org; Mon, 03 Mar 2014 20:30:46 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.82) (envelope-from ) id 1WKZVc-00050e-QS for rsgb_lf_group@blacksheep.org; Mon, 03 Mar 2014 20:30:45 +0000 Received: from sb.abelian.org (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id E5007327560 for ; Mon, 3 Mar 2014 20:29:21 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by sb.abelian.org (Postfix) with ESMTP id 8D5E028A0A6A for ; Mon, 3 Mar 2014 20:30:41 +0000 (UTC) Message-ID: <5314E671.3030709@abelian.org> Date: Mon, 03 Mar 2014 20:30:41 +0000 From: Paul Nicholson User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <5314C1EC.6090800@abelian.org> <5314CBA9.3090007@freenet.de> In-Reply-To: <5314CBA9.3090007@freenet.de> X-Spam-Score: 0.7 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: I ran some tests using Bob's signal from last night using various sferic blanking thresholds http://abelian.org/vlf/tmp/29499_140303a.png I've given the threshold in dB as you would set into Spectrum Lab. This is the ratio of the trigger threshold to the mean signal level (maybe SL uses RMS, but not much difference). [...] Content analysis details: (0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [217.72.171.49 listed in list.dnswl.org] 0.7 SPF_NEUTRAL SPF: sender does not match SPF record (neutral) X-Scan-Signature: 6ffbd2c9950b634d6cc91f9565b01a8b Subject: Re: LF: VLF weak signals and sferic blanking Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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=0.9 required=5.0 tests=FROM_ENDS_IN_NUMS 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 I ran some tests using Bob's signal from last night using various sferic blanking thresholds http://abelian.org/vlf/tmp/29499_140303a.png I've given the threshold in dB as you would set into Spectrum Lab. This is the ratio of the trigger threshold to the mean signal level (maybe SL uses RMS, but not much difference). The percentage indicates the proportion of time that the blanker is active. The high threshold of 30dB is enough to bring the carrier above noise. Morse was being transmitted and with 10dB threshold the sidebands are starting to show quite clearly. I don't think any more signal features appear with settings lower than 10dB but maybe the noise floor drops a little. The setting I've been using at 29499 is 3.5dB. At lower VLF I use 1.6dB. It looks like we can be less aggressive at these higher frequencies. The input bandwidth to the blanker is 28 - 31kHz and there are no continuous signals there at my location. One related point - ensure that nothing in the signal chain (analogue or digital) is clipping the signal, except maybe the occasional sferic. In particular if the mains hum hits a clipping threshold anywhere along the way, it will intermod with the noise and prevent any decent reception. Instead of a nice smooth background hiss, it will sound like a rasping buzz at all frequencies. -- Paul Nicholson --