Return-Path: Received: from mtain-mh09.r1000.mx.aol.com (mtain-mh09.r1000.mx.aol.com [172.29.96.221]) by air-ma07.mail.aol.com (v127_r1.1) with ESMTP id MAILINMA071-b52c4b8ce35d1f8; Tue, 02 Mar 2010 05:07:25 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mh09.r1000.mx.aol.com (Internet Inbound) with ESMTP id A7F2E38000949; Tue, 2 Mar 2010 05:07:23 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NmOzc-0002M5-Di for rs_out_1@blacksheep.org; Tue, 02 Mar 2010 10:06:20 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NmOzc-0002Lw-1S for rsgb_lf_group@blacksheep.org; Tue, 02 Mar 2010 10:06:20 +0000 Received: from parrot.netcom.co.uk ([217.72.171.49]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NmOzZ-0005Mo-UU for rsgb_lf_group@blacksheep.org; Tue, 02 Mar 2010 10:06:20 +0000 Received: from abelian.netcom.co.uk (i-194-106-52-83.freedom2surf.net [194.106.52.83]) by parrot.netcom.co.uk (Postfix) with ESMTP id DD0D0228044 for ; Tue, 2 Mar 2010 10:03:54 +0000 (GMT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by abelian.netcom.co.uk (8.13.1/8.13.1) with ESMTP id o22A6ArA012866 for ; Tue, 2 Mar 2010 10:06:10 GMT Message-ID: <4B8CE312.7090904@abelian.org> Date: Tue, 02 Mar 2010 10:06:10 +0000 From: Paul Nicholson User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: In-Reply-To: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Re: 9kHz noise level 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d60dd4b8ce35b3938 X-AOL-IP: 193.82.116.20 X-Mailer: Unknown (No Version) It is encouraging to see interest in amateur tx experiments in the VLF band. Calculations suggest that ranges of 100km or more would be possible with QRSS given about 1mW ERP which is not an unreasonable target for a determined amateur. The limiting factor is the VLF background noise, which at 9kHz is typically 5uV/m/sqrt(Hz) or 30fT/sqrt(Hz), give or take a few dB of diurnal and seasonal variation. Here is a live spectrum display of the band 8790Hz, +/- 0.5Hz with 0.005Hz resolution, http://abelian.org/vlf/live/nb.png as received at Todmorden, UK, 53.703N 2.072W, on an east-west loop antenna. System sensitivity is about 0.03fT in the bin bandwidth but the VLF background noise floor is at about 2fT. The above spectrum is implemented with a bank of Goertzel filters and sferics are removed before the filters. The spike is a test signal at 1V RMS from a laptop soundcard line output into a 700uH 25 turn loop enclosing 0.2 sq metres, located about 180m from the rx loop. The test signal should be about 5fT at the rx site but appears a little stronger for some reason. Here is the full VLF spectrum rxed at Todmorden on orthogonal loops, http://abelian.org/vlf/spectrum.shtml and there is a live audio/video display at http://abelian.org/vlf/test.html Looking forward with great interest to further news of transmitting experiments from Stefan DK7FC, Markus DF6NM, Jacek SQ5BPF, et al. -- Paul Nicholson http://abelian.org/vlf Todmorden, UK. --