Return-Path: Received: (qmail 27000 invoked from network); 1 Feb 2003 12:51:50 -0000 Received: from netmail01.services.quay.plus.net (212.159.14.219) by mailstore with SMTP; 1 Feb 2003 12:51:50 -0000 Received: (qmail 20933 invoked by uid 10001); 1 Feb 2003 12:51:49 -0000 Received: from post.thorcom.com (193.82.116.70) by netmail01.services.quay.plus.net with SMTP; 1 Feb 2003 12:51:49 -0000 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.12) id 18ex6e-0001Vp-00 for rsgb_lf_group-outgoing@blacksheep.org; Sat, 01 Feb 2003 12:50:48 +0000 Received: from [24.153.64.2] (helo=smtp.comcast.net) by post.thorcom.com with esmtp (Exim 4.12) id 18ex6e-0001Vg-00 for rsgb_lf_group@blacksheep.org; Sat, 01 Feb 2003 12:50:48 +0000 Received: from yourw92p4bhlzg (pcp02064100pcs.nrockv01.md.comcast.net [68.83.215.165]) by mtaout04.icomcast.net (iPlanet Messaging Server 5.2 HotFix 1.09 (built Jan 7 2003)) with SMTP id <0H9M00CRQRMUN2@mtaout04.icomcast.net> for rsgb_lf_group@blacksheep.org; Sat, 01 Feb 2003 07:49:43 -0500 (EST) Date: Sat, 01 Feb 2003 07:49:48 -0500 From: "Ralph Lane" To: rsgb_lf_group@blacksheep.org Message-ID: <000e01c2c9f0$67d15020$0000a398@yourw92p4bhlzg> MIME-Version: 1.0 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Mailer: Microsoft Outlook Express 6.00.2720.3000 X-Priority: 3 X-MSMail-Priority: Normal References: <5.1.0.14.0.20030131161755.00aef0b8@gemini.herts.ac.uk> Subject: LF: Re: RX loop designs Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=0.6 required=6.0tests=FROM_ENDS_IN_NUMS,QUOTED_EMAIL_TEXT,REFERENCES, SPAM_PHRASE_00_01,USER_AGENT_OEversion=2.43 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rsgb_lf_group-outgoing@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Jim, sounds like interesting designs. I would like a copy. Thanks, Ralph ----- Original Message ----- From: "James Moritz" To: Sent: Saturday, February 01, 2003 6:32 AM Subject: LF: RX loop designs > Dear LF Group, > > With the recent chatter about LF loops, I finally got round to writing up 3 > of my receiving loop designs, which I have been using for the last year or > so. They seem to be significantly different to the designs other people > have come up with, and work well, so could be of interest. > > The usual problem with a tuned loop is that the bandwidth is very narrow, > so remote tuning is needed. Resistively loading the loop increases BW, but > reduces the loop output and SNR, so a bigger loop is needed, and also > out-of-band selectivity is reduced. My idea was to add an additional tuned > circuit coupled to the loop to produce a bandpass response, which can be > designed to give a flat-topped or slightly double-peaked response covering > the whole 136kHz band without re-tuning. This has turned out to work well, > and the article describes one 1m^2 loop with a bandwidth of about 4kHz, and > a 2m x 2m loop using a single turn of tubing with a bandwidth of about > 18kHz. With the simple pre-amp also described, the noise floor of both > these antennas is well below the band noise even on a quiet day. > > The article also includes a wideband loop based on a low-pass rather than > bandpass design, which covers 10kHz -200kHz, also a single turn 2m x 2m > loop. This is slightly less sensitive than the bandpass designs, but more > than adequate for general use over the LF/VLF range. The relationship > between field strength and loop output for this antenna is predictable, so > it can also be used for field strength measurement. > > The article I have written is 5 pages, with several diagrams, and is a .pdf > file of about 340kB. It is too big for the reflector, but if you are > interested, let me know, and I will e-mail it to you as an attachment. > > Cheers, Jim Moritz > 73 de M0BMU > > >