Return-Path: X-Spam-DCC: paranoid 1233; Body=3 Fuz1=3 Fuz2=3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=BAYES_00,FORGED_RCVD_HELO, RATWARE_GECKO_BUILD autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id sB6JlldN021723 for ; Sat, 6 Dec 2014 20:47:47 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1XxLED-0002aU-Ih for rs_out_1@blacksheep.org; Sat, 06 Dec 2014 19:41:17 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1XxLED-0002aL-2p for rsgb_lf_group@blacksheep.org; Sat, 06 Dec 2014 19:41:17 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.84) (envelope-from ) id 1XxLDu-0003MO-3s for rsgb_lf_group@blacksheep.org; Sat, 06 Dec 2014 19:41:15 +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 D1FC5327408 for ; Sat, 6 Dec 2014 19:40:13 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by sb.abelian.org (Postfix) with ESMTP id 02C1828A0F4A for ; Sat, 6 Dec 2014 19:40:55 +0000 (UTC) Message-ID: <54835BC6.9030700@abelian.org> Date: Sat, 06 Dec 2014 19:40:54 +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: <3393F5E9C750444D91470512A209D34E@White> In-Reply-To: <3393F5E9C750444D91470512A209D34E@White> X-Scan-Signature: 046f068074e745d5c60ca47deee9b503 Subject: Re: VLF: 8270 Hz Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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 X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 1423 > Uwe, back again this afternoon? Some signals on the band would be handy. Trying to test new E-field rx against old with the two planted side by side on a bleak moorland hillside. Needed some weak signal so made up a little near field tx starting with 280V to a 'long' wire, 3m long 1m high. 150m away from the rx with a small plantation of trees in between but the signal was way too strong. Ended up with a few volts from a sound card onto the wire. New rx design models well and it tests pretty good on the bench, but when deployed performs poorly. Noise floor is consistently 1.4dB higher on the new rx than the old, and the old one is quite noisy anyway. I've no idea where the noise is coming from. Thermal noise of ground resistance? No, the new rx has a better ground. It's a black art, this stuff. A VLF rx is just an audio amplifier, how hard can that be? The antenna too is fighting back. Despite sealing with O-rings, flexible sealant, and layers of self amalgamating tape, it still manages to fill with water after a few days of rain. When I eventually get this thing running and calibrated, the spectrogram at http://abelian.org/vlf/fbins.shtml will gain a dB or two sensitivity and be steerable modulo 360 degrees instead of 180. -- Paul Nicholson --