Return-Path: Received: from mtain-dh01.r1000.mx.aol.com (mtain-dh01.r1000.mx.aol.com [172.29.65.21]) by air-dd03.mail.aol.com (v129.4) with ESMTP id MAILINDD033-86594ced3b60299; Wed, 24 Nov 2010 11:20:48 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh01.r1000.mx.aol.com (Internet Inbound) with ESMTP id 881F7380001B0; Wed, 24 Nov 2010 11:20:46 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PLI4h-0006vp-8A for rs_out_1@blacksheep.org; Wed, 24 Nov 2010 16:20:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PLI4g-0006vg-S7 for rsgb_lf_group@blacksheep.org; Wed, 24 Nov 2010 16:20:02 +0000 Received: from relay.uni-heidelberg.de ([129.206.100.212]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PLI4f-00061s-7Q for rsgb_lf_group@blacksheep.org; Wed, 24 Nov 2010 16:20:02 +0000 Received: from freitag.iup.uni-heidelberg.de (freitag.iup.uni-heidelberg.de [129.206.29.204]) by relay.uni-heidelberg.de (8.14.1/8.14.1) with ESMTP id oAOGJK0Z020899 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 24 Nov 2010 17:19:20 +0100 Received: from [129.206.29.99] (pc99.iup.uni-heidelberg.de [129.206.29.99]) by freitag.iup.uni-heidelberg.de (8.12.11.20060308/8.11.2) with ESMTP id oAOGK0uh011566 for ; Wed, 24 Nov 2010 17:20:00 +0100 Message-ID: <4CED1834.4020702@iup.uni-heidelberg.de> Date: Wed, 24 Nov 2010 14:50:44 +0100 From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <373372.70115.qm@web28506.mail.ukl.yahoo.com> <4CEAE16C.5030101@iup.uni-heidelberg.de> <294616.39798.qm@web28506.mail.ukl.yahoo.com> <4CEBEEDF.6000301@iup.uni-heidelberg.de> <001d01cb8bc3$438cb6d0$4001a8c0@lark> In-Reply-To: <001d01cb8bc3$438cb6d0$4001a8c0@lark> X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,RATWARE_GECKO_BUILD=1.426 Subject: Re: LF: VLF G3XIZ - QRT Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G x-aol-sid: 3039ac1d41154ced3b5e2b28 X-AOL-IP: 195.171.43.25 X-Mailer: Unknown (No Version) Chris, Alan, LF, Am 24.11.2010 11:26, schrieb Alan Melia: > Chris I dont think slowing the drive edges will be the answer. This is a > switching PA and needs to switch quickly otherwise the dissipation will rise > rapidly. Exactly :-) > Any slowing edge will have to be on the drain side in the form of > a low pass filter. Unstable loads will lead to excessive voltages at the > drain which cause breakdown even if the voltage rating is 4 times the supply > (the usual spec.) Why a transformer the tranformer arced is the question, > there should not be that high a voltage there Exactly! I rather assume that the transformer has had to less primary turns and went into saturation on that frequency. Then it became hot and some turns' insulations are molten. When the temperature increases to very high values, the relative permittivity decreases, so the L, so the currents can become excessive and so it was probably an "over-power death" of the FETs. When applying a primary coupling winding directly on the loading coil, the PA impedance can be transformed there, without anything that can go into saturation. Just the wires should be kept short between PA and coil. Just like Tesla-transformeers are fed with a primary winding of some turns, something between 5 and 20 probably. The galvanic decoupling may be an additional advantage in some cases. 73, Stefan