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 vB781OfG032679 for ; Thu, 7 Dec 2017 09:01:27 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1eMr35-00088O-R3 for rs_out_1@blacksheep.org; Thu, 07 Dec 2017 07:56:51 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1eMr35-00088F-8i for rsgb_lf_group@blacksheep.org; Thu, 07 Dec 2017 07:56:51 +0000 Received: from porthos.netcom.co.uk ([217.72.171.73]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eMr32-0007cL-IL for rsgb_lf_group@blacksheep.org; Thu, 07 Dec 2017 07:56:50 +0000 X-DKIM-Result: Domain=abelian.org Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=abelian.org ; s=default; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:To:Subject:Sender:Reply-To:Cc: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=VDzqooWPF82eKPbMb4JD8WvDSZBy5wdn9OvNX3+TeH4=; b=V+Wb5evMgj6Hp3u0v+8lWcD120 tTdqpMch/wO+Qz39OC3Xj1Yo2CC3J5HDa/u4UsV9oM6w+u7OTPmI7W7TLQIkMUImSmlau4zsMCFG3 0cvJ3jv4S8vOqLIswPMG6AyQjiMwKLMk7NEm4vQdUvJGa10rMAoZk7axvC/TBCUuxDp8=; Received: from i-194-106-52-83.freedom2surf.net ([194.106.52.83]:41643 helo=pn.abelian.org) by porthos.netcom.co.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eMr30-0004be-Uh for rsgb_lf_group@blacksheep.org; Thu, 07 Dec 2017 07:56:47 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by pn.abelian.org (Postfix) with ESMTP id 3CA85400254 for ; Thu, 7 Dec 2017 07:56:46 +0000 (UTC) To: rsgb_lf_group@blacksheep.org References: <4d96a9d4-5f22-7650-872b-6344e9aea8e3@abelian.org> <5A19FF75.7080801@posteo.de> <5A1FFE7C.9050703@posteo.de> <5A226B0C.3080701@posteo.de> <579355A36AEE9D4FA555C45D556003AB9AAB0EB9@servigilant.vigilant.local> <5A25C304.3050607@posteo.de> <5A271218.9040803@posteo.de> <1d9b2c0d-5fd5-066d-8f66-e85a79f88f16@abelian.org> From: Paul Nicholson Message-ID: <876ba966-4bd3-d682-123c-aae9c39ee63b@abelian.org> Date: Thu, 7 Dec 2017 07:56:46 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - porthos.netcom.co.uk X-AntiAbuse: Original Domain - blacksheep.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - abelian.org X-Get-Message-Sender-Via: porthos.netcom.co.uk: authenticated_id: catchall@abelian.org X-Authenticated-Sender: porthos.netcom.co.uk: catchall@abelian.org X-Spam-Score: 0.0 (/) 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 the administrator of that system for details. Content preview: > what is the reason to use a 3kHz filter before the noise > blanker and not a narrower one? For lowest noise floor out of the blanker, narrower is better so that less out-of-band energy is going into the blanker. The blanker is an amplitude modulator with a random modulating signal and thus creates random sidebands around every frequency component going in, which averages out to a raised noise floor. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: bb61bee384896e075004ae5ec954ddd2 Subject: Re: VLF: First VLF detection DL > EA Content-Type: text/plain; charset=utf-8; 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 > what is the reason to use a 3kHz filter before the noise > blanker and not a narrower one? For lowest noise floor out of the blanker, narrower is better so that less out-of-band energy is going into the blanker. The blanker is an amplitude modulator with a random modulating signal and thus creates random sidebands around every frequency component going in, which averages out to a raised noise floor. Too narrow and the sferics become stretched in time and reduced in amplitude by the filter. They become harder to discern against the threshold and the blanking duration becomes longer than necessary. So wider is better in that respect. Somewhere then, in the middle there is an optimum. Fortunately a broad optimum. I standardised on 3kHz after some trial and error at about 9kHz. Perhaps at higher frequencies a narrower filter might work better. Some trials are called for and I can imagine a shell script already being prepared at SQ5BPF. -- Paul Nicholson --