Return-Path: Received: (qmail 12327 invoked from network); 19 May 1999 17:18:33 +0100 Received: from magnet.plus.net.uk (HELO magnet.force9.net) (195.166.128.26) by guiness.force9.net with SMTP; 19 May 1999 17:18:33 +0100 Received: (qmail 22452 invoked from network); 19 May 1999 15:54:31 -0000 Content-Transfer-Encoding: 8bit Received: from punt.unica.co.uk (194.75.183.60) by magnet.plus.net.uk with SMTP; 19 May 1999 15:54:31 -0000 Received: from troy.blacksheep.org ([194.75.183.50] ident=root) by punt.unica.co.uk with esmtp (Exim 2.00 #2) id 10k8cr-0001MV-00; Wed, 19 May 1999 16:51:21 +0100 X-Priority: 3 X-MSMail-Priority: Normal Received: (from root@localhost) by troy.blacksheep.org (8.6.12/8.6.12) id PAA07384 for rsgb_lf_group-outgoing; Wed, 19 May 1999 15:47:26 GMT Received: from post.thorcom.com (root@post.unica.co.uk [194.75.183.70]) by troy.blacksheep.org (8.6.12/8.6.12) with ESMTP id PAA07380 for ; Wed, 19 May 1999 15:47:24 GMT Received: from fm215.facility.pipex.com ([194.131.104.225]) by post.thorcom.com with esmtp (Exim 2.04 #3) id 10k8nG-0002Gs-00 for rsgb_lf_group@blacksheep.org; Wed, 19 May 1999 17:02:06 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from walter (usern823.uk.uudial.com [193.149.86.94]) by fm215.facility.pipex.com (8.8.6/8.8.6) with SMTP id QAA22270 for ; Wed, 19 May 1999 16:43:58 +0100 (BST) Message-ID: <199905191543.QAA22270@fm215.facility.pipex.com> X-Sender: blanch@mailhost.pncl.co.uk X-Mailer: QUALCOMM Windows Eudora Pro Version 4.0 Date: Wed, 19 May 1999 16:46:36 +0100 To: rsgb_lf_group@blacksheep.org From: "Walter Blanchard" Subject: LF: "RF Design" magazine article MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org The April 1999 issue of the US "RF Design" magazine has an article "Understanding range limitations for low-frequency unlicensed transmissions" about FCC "Part 15" transmitters for local data links that are so low power they don't need licensing. One of the bands they use is 160-190 kHz limited to a DC power INPUT to the amplifier of 1 watt and an antenna no bigger than 15 metres. The author calculates a range of 12 kms if everything is optimum (including zero ground loss!) but he also gets a range of 375 kms for a one-tenth watt (DC input) transmitter on 1705 kHz using a 3 metre antenna so I guess it's all a bit suspect. Anyway, he gives the formulae and makes some pertinent points about transmission path and background noise problems so it might be a handy summary for anyone new to LF. Walter G3JKV.