Envelope-to: dave@picks.force9.co.uk Delivery-date: Mon, 03 Oct 2005 11:08:51 +0100 Received: by pih-mxcore06.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EMNFZ-0006Tq-Oh for dave@picks.force9.co.uk; Mon, 03 Oct 2005 11:08:51 +0100 Received: from post.thorcom.com ([193.82.116.20]) by pih-mxcore06.plus.net with esmtp (PlusNet MXCore v2.00) id 1EMNFZ-0006Th-LF for dave@picks.force9.co.uk; Mon, 03 Oct 2005 11:08:49 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EMNF4-0002Lm-Je for rs_out_1@blacksheep.org; Mon, 03 Oct 2005 11:08:18 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EMNF4-0002Ld-63 for rsgb_lf_group@blacksheep.org; Mon, 03 Oct 2005 11:08:18 +0100 Received: from [194.203.13.70] (helo=viruswall.astrium.eads.net) by relay1.thorcom.net with esmtp (Exim 4.51) id 1EMNpU-0006wu-RJ for rsgb_lf_group@blacksheep.org; Mon, 03 Oct 2005 11:45:59 +0100 Received: from mms12031.pth.uk.astrium.corp ([194.35.68.222]) by viruswall.astrium.eads.net with InterScan Messaging Security Suite; Mon, 03 Oct 2005 11:07:57 +0100 Received: by mms12031.pth.uk.astrium.corp with Internet Mail Service (5.5.2650.21) id <4FT3RK05>; Mon, 3 Oct 2005 11:08:00 +0100 Message-ID: From: "OSBORN, Chris" To: "LF Group (E-mail)" Date: Mon, 3 Oct 2005 11:08:03 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Subject: LF: Advice (again) please Content-Type: text/plain; charset=iso-8859-1; format=flowed 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) Content-transfer-encoding: 8bit I'm still beavering away on my new TX and now have stopped blowing up the PA devices (fingers crossed). I've incorporated some of the suggestions gratefully received:- - Higher voltage FETs - IRF630's - gate resistors to prevent vhf oscillation I have also changed from transformer drive to using a 4426 driver IC. I'm generating 100 watts into my 50 ohm dummy load but only getting an efficiency of about 50%. The output transformer toroidal core is getting quite hot and I suspect that it's permeability is too low as the capacitance required to bring it to resonance is far higher than those of published designs in the LF Experimenter's handbook, using the same number of turns. These capacitors are running very hot too (as mentioned by PA0SE in his LFEH article). Has anyone a spare 3C85 toroid suitable for a PA stage which they would sell to me ? Alternatively I've looked in the RS catalogue but am not sure what is a suitable type. They quote a parameter 'AL' ( example 3225 nH) From my old college days I remember uo and ur but what is 'AL' ? 73 Chris G3XIZ This email is for the intended addressee only. If you have received it in error then you must not use, retain, disseminate or otherwise deal with it. Please notify the sender by return email. The views of the author may not necessarily constitute the views of EADS Astrium Limited. Nothing in this email shall bind EADS Astrium Limited in any contract or obligation. EADS Astrium Limited, Registered in England and Wales No. 2449259 Registered Office: Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2AS, England