Return-Path: Received: (qmail 2034 invoked from network); 25 Nov 2002 16:53:59 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 25 Nov 2002 16:53:59 -0000 Content-Transfer-Encoding: 8bit Received: (qmail 13280 invoked from network); 25 Nov 2002 16:53:58 -0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 25 Nov 2002 16:53:58 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18GMSy-0003mE-00 for rsgb_lf_group-outgoing@blacksheep.org; Mon, 25 Nov 2002 16:52:12 +0000 Received: from [134.58.10.57] (helo=mail3.cc.kuleuven.ac.be) by post.thorcom.com with esmtp (Exim 4.10) id 18GMSx-0003ly-00 for rsgb_lf_group@blacksheep.org; Mon, 25 Nov 2002 16:52:11 +0000 Received: from dell-rik.fys.kuleuven.ac.be (pc-10-33-165-177.fys.kuleuven.ac.be [10.33.165.177]) by mail3.cc.kuleuven.ac.be (8.12.1/8.12.1) with ESMTP id gAPGpe27031426 for ; Mon, 25 Nov 2002 17:51:41 +0100 Message-ID: <5.1.0.14.0.20021125171906.00b9d028@pb623250.kuleuven.be> X-Sender: pb623250@pb623250.kuleuven.be X-Mailer: QUALCOMM Windows Eudora Version 5.1 Date: Mon, 25 Nov 2002 17:58:05 +0100 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" In-reply-to: <001d01c29475$f77f6140$0500a8c0@charter.net> References: <3DE1338E.2F1E9274@att.net> <000801c29474$a4e23300$1ee086d4@erica> MIME-Version: 1.0 Subject: LF: loop antenna Content-Type: text/plain; charset=us-ascii; format=flowed X-Spam-Status: No, hits=-0.5 required=5.0tests=IN_REP_TO,REFERENCES,SPAM_PHRASE_00_01version=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Hello group, I am about to put up a transmitting loop antenna. Dimensions will be 23m long and 15m high. Thanks to Dick (PA0SE) I could achieve a wheel of 7mm litz wire, so wire losses should be minimized (about 0.04 Ohm). Some questions : - What distance should I keep to the ground ? It's a tradeoff between loop area (and thus radiation resistance) and loss resistance. - What distance should I keep to the greenery (birch trees) ? Same tradeoff as above but also keeping in mind that the trees are used as antenna support and that the 7mm litz wire is rather heavy stuff (so from the mechanical point of view it would be best to have the wire just hanging on the branches). - How to match the antenna ? As it is an experimental setup I would tend to keep the resonance tuning (= series capacitor) and impedance matching (= transformer) separated. Any experience with a 100/1 .. 400/1 transformer (matching 50 Ohm of the TX to 0.1 .. 0.4 Ohm of the loop - at least I hope to get losses that low). Some quick and dirty calculations : If the lower wire is 1m above ground then the loop area is 322m^2 and radiation resistance is 0.14 .. 0.28 milli-Ohm (let's assume 0.2 milli-Ohm). 1. if Rloss = 1 Ohm and 450W RF power -> antenna current = 21A -> EIRP = 135mW 2. if Rloss = 0.5 Ohm and 450W RF power -> antenna current = 30A -> EIRP = 370mW 3. if Rloss = 0.2 Ohm and 450W RF power -> antenna current = 47A -> EIRP = 675mW 4. to get 1W EIRP with 450W RF power I would need 71A antenna current and losses as low as 0.09 Ohm 73, Rik ON7YD