Return-Path: <owner-rsgb_lf_group@blacksheep.org> X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=0.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 X-Spam-DCC: wuwien: mailn 1290; Body=3 Fuz1=3 Fuz2=3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v8AICPeM019183 for <sq5bpf@lipkowski.org>; Sun, 10 Sep 2017 20:12:30 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1dr6dF-0004uF-Ec for rs_out_1@blacksheep.org; Sun, 10 Sep 2017 19:06:57 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1dr6cP-0004u6-RM for rsgb_lf_group@blacksheep.org; Sun, 10 Sep 2017 19:06:05 +0100 Received: from lethe.lipkowski.org ([178.32.151.135] helo=lipkowski.org) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from <sq5bpf@lipkowski.org>) id 1dr6cM-0005L7-Sb for rsgb_lf_group@blacksheep.org; Sun, 10 Sep 2017 19:06:04 +0100 Received: from mailn.lipkowski.org (localhost [127.0.0.1]) by lipkowski.org (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id v8AI6YMC019150 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT) for <rsgb_lf_group@blacksheep.org>; Sun, 10 Sep 2017 20:06:35 +0200 Received: from localhost (sq5bpf@localhost) by mailn.lipkowski.org (8.14.4/8.14.4/Submit) with ESMTP id v8AI6U41019147 for <rsgb_lf_group@blacksheep.org>; Sun, 10 Sep 2017 20:06:34 +0200 X-Authentication-Warning: mailn.lipkowski.org: sq5bpf owned process doing -bs Date: Sun, 10 Sep 2017 20:06:30 +0200 (CEST) From: Jacek Lipkowski <sq5bpf@lipkowski.org> To: rsgb_lf_group@blacksheep.org In-Reply-To: <6a4f2233-82b4-1264-6cad-0739ad154ed1@abelian.org> Message-ID: <alpine.DEB.2.11.1709101949330.734@mailn.lipkowski.org> References: <15e3d8ac066-c0a-2fad5@webjas-vab092.srv.aolmail.net> <ea5c681a-730a-0a82-8bd3-0de7333de013@abelian.org> <6a4f2233-82b4-1264-6cad-0739ad154ed1@abelian.org> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.75 X-Scanned-By: MIMEDefang 2.75 on 10.1.3.10 X-Scan-Signature: 5c335215f1b3de26d890ee84d49616ce Subject: Re: VLF: E-field receivers in Todmorden Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed 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 Status: O X-Status: X-Keywords: X-UID: 12564 On Sun, 10 Sep 2017, Paul Nicholson wrote: > Merging the currents from multiple front-end devices is a > conventional way to achieve ultra low noise and this looks > like a good implementation. > > I tried this technique with two devices but the doubling of the > input capacitance reduced the signal by as much as the noise > was lowered, no overall benefit (in fact slightly worse). > This kind of thing shows up when you refer the system noise > to field strength V/m instead of just input voltage. you would also need to have a proportionally bigger antenna (2x capacitance for 2 fets etc), OR you can use multiple e-probes, each with it's own fet :) the latter can be easier to implement in some situations, for example using 8 beer cans for eprobes each with it's own fet might be simpler than a beer keg and 8 fets in parallel, both configurations should theoretically give 9dB less noise (assuming that the capacitance of 8 beer cans is equivalent to that of a keg of course). the added benefit is that 50Hz noise isn't in-phase in different locations near homes (unless everything is fed from the same phase), some some of it will cancel out. it's a concept i've been thinking about for some time now, but never got around to implement it. even it you have the antennas quite far apart, you don't need to care about phasing at kHz frequencies. VY 73 Jacek / SQ5BPF