Return-Path: Received: (qmail 12031 invoked from network); 18 Nov 1999 16:39:56 +0000 Received: from unknown (HELO cask.force9.net) (195.166.128.29) by guiness.force9.net with SMTP; 18 Nov 1999 16:39:56 +0000 Received: (qmail 108 invoked from network); 18 Nov 1999 16:39:59 -0000 Content-Transfer-Encoding: 8bit Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by cask.force9.net with SMTP; 18 Nov 1999 16:39:59 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 11oUG1-0003nF-00 for rsgb_lf_group-outgoing@blacksheep.org; Thu, 18 Nov 1999 16:18:01 +0000 X-Priority: 3 X-MSMail-Priority: Normal Received: from mailserv.cc.kuleuven.ac.be ([134.58.8.44]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 11oUG0-0003nA-00 for rsgb_lf_group@blacksheep.org; Thu, 18 Nov 1999 16:18:00 +0000 Received: from LCBD15.fys.kuleuven.ac.be (LCBD15.fys.kuleuven.ac.be [134.58.80.15]) by mailserv.cc.kuleuven.ac.be (8.9.0/8.9.0) with SMTP id RAA16508 for ; Thu, 18 Nov 1999 17:25:10 +0100 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Message-ID: <3.0.1.16.19991118181720.4aaf8b32@mail.cc.kuleuven.ac.be> X-Sender: pb623250@mail.cc.kuleuven.ac.be X-Mailer: Windows Eudora Pro Version 3.0.1 (16) Date: Thu, 18 Nov 1999 18:17:20 To: rsgb_lf_group@blacksheep.org From: "Rik Strobbe" Subject: LF: dummyload MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: For test-puposes I needed a dummyload that could withstand 450W on 136kHz for some minutes. Having some 470 Ohm / 25 Watt wirewound resistors in the junkbox I put 9 of them in parallel and measured 52 Ohm with my DVM. Next I took it to my work and checked it there on the impedance analyzer : at 137kHz it was 51.6 + j1.3 Ohms, so more than good enough. Although 9 x 25 = 225W they withstand 450W for about 2 minutes before it starts 'smelling'. After several of these 'mistreatements' I checked it again on the impedance analyzer and it was still 51.6 + j1.3 Ohms, so overheating the resistors for a shot period does not seem to affect it. So, if you need a high power 50 Ohm dummyload but don't want to spend too much money on it : just parralel a bunch of high-power wirewound resistors, it works fine on 136kHz. For a short period (few minutes) they even withstand the double power they are rated for. One final remark : don't put the resistors too close together or the middle one(s) will become too hot. I kept all resistors about 2.5cm (1 inch) apart. 73, Rik ON7YD