Return-Path: Received: (qmail 14184 invoked from network); 2 Jan 2001 09:37:26 -0000 Received: from unknown (HELO murphys-inbound.servers.plus.net) (212.159.14.225) by extortion.plus.net with SMTP; 2 Jan 2001 09:37:26 -0000 Received: (qmail 16843 invoked from network); 2 Jan 2001 09:40:01 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by murphys with SMTP; 2 Jan 2001 09:40:01 -0000 Content-Transfer-Encoding: 8bit Received: from majordom by post.thorcom.com with local (Exim 3.16 #1) id 14DNp7-0002rZ-00 for rsgb_lf_group-outgoing@blacksheep.org; Tue, 02 Jan 2001 09:33:41 +0000 Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.16 #1) id 14DNp5-0002rT-00 for rsgb_lf_group@blacksheep.org; Tue, 02 Jan 2001 09:33:40 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id JAA26254; Tue, 2 Jan 2001 09:34:21 GMT Received: (qmail 3000 invoked from network); 2 Jan 2001 10:27:54 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 2 Jan 2001 10:27:54 -0000 Received: by gauntlet.mail.dera.gov.uk; id KAA08200; Tue, 2 Jan 2001 10:21:02 GMT Received: from unknown(10.71.64.31) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma007844; Tue, 2 Jan 01 10:20:17 GMT Received: from frn-gold-1.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Tue, 2 Jan 2001 09:35:05 +0000 Received: by frn-gold-1.dera.gov.uk with Internet Mail Service (5.0.1460.8) id ; Tue, 2 Jan 2001 09:32:37 -0000 Message-ID: <65AECDF1F89AD411900400508BFC869F0D74C5@pdw-mail-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: RE: Loop Antennas for RX and TX Date: Tue, 2 Jan 2001 09:32:46 -0000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.0.1460.8) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Try to get hold of a copy of the original Mk1 LF Source Book - I covered transmitting loops in there in some detail - before realising they are not the way to go on LF ! Unless you can erect a loop with a huge area (100s of m^2 at these frequencies) you will always do better with an E field antenna than an H loop. Radiation resistance / efficeincy is proportional to the fourth power of loop dimensions (square of loop area) What do you mean by small - my garden is just 14m long x 6 wide and have a 7m high tee antenna with a radiation efficiency around -36dB and feed impedance 100 - 130 ohms - although being on heavy clay of good conductivity this is rather better than may otherwise be achieved. On a receiving loop , why is there such a fuss about preamps ? A tuned 1m square loop with several turns of wire, coupled with one turn (or any other suitable matching network) to a 50 ohm input provides more than enough signal for most receivers except perhaps the very deafest operating outside their specified frequency range. Andy G4JNT > 1) Does anyone have any pointers to or formula for a loop aerial for > transmitting on 136?. Or other ideas on radiating out of a > very small back > yard? > > and > > 2) Having built an RX loop based upon the G3LNP design I am > interested in > receiving recent posts regarding the fet input pre-amp / > modifications. Is > there any reason not to use an op-amp? > > -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.