Envelope-to: dave@picks.force9.co.uk Delivery-date: Wed, 28 Sep 2005 11:41:54 +0100 Received: by pih-mxcore10.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EKZNp-0000Vs-TJ for dave@picks.force9.co.uk; Wed, 28 Sep 2005 11:41:54 +0100 Received: from post.thorcom.com ([193.82.116.20]) by pih-mxcore10.plus.net with esmtp (PlusNet MXCore v2.00) id 1EKZNp-0000Vm-PA for dave@picks.force9.co.uk; Wed, 28 Sep 2005 11:41:53 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EKZNj-0004py-G7 for rs_out_1@blacksheep.org; Wed, 28 Sep 2005 11:41:47 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EKZNi-0004pl-W2 for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2005 11:41:46 +0100 Received: from smtp809.mail.ukl.yahoo.com ([217.12.12.199]) by relay1.thorcom.net with smtp (Exim 4.51) id 1EKZwG-0007Co-AR for rsgb_lf_group@blacksheep.org; Wed, 28 Sep 2005 12:17:33 +0100 Received: (qmail 98747 invoked from network); 28 Sep 2005 10:41:36 -0000 Received: from unknown (HELO Main) (Alan.Melia@213.122.198.226 with login) by smtp809.mail.ukl.yahoo.com with SMTP; 28 Sep 2005 10:41:35 -0000 Message-ID: <000c01c5c419$283add20$e2c67ad5@Main> From: "Alan Melia" To: rsgb_lf_group@blacksheep.org References: Date: Wed, 28 Sep 2005 11:41:14 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Subject: LF: Re: Advice will be gratefully received Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit 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) Chris Ah according to my notes the peak voltage if you verge on Class E can approach 4 times the supply.....I think that might be your problem. This is necessary to allow a bit of headroom when tuning as "odd" reactances at the drain will cause the peak drain voltage to soar. I use 200V devices up to about 40 -45 volts supply and 500V above that. If you are transformer driving I assume you have a negative voltage clamp (diode) Alan G3NYK ----- Original Message ----- From: "OSBORN, Chris" To: "LF Group (E-mail)" Sent: 28 September 2005 10:43 Subject: LF: Advice will be gratefully received > > > > The PA FET's in my new home brew transmitter keep exploding ! > > I'm using push-pull IRF520's rated at 100 V Vds and my supply is 30 > volts. > I am careful not to exceed the V gs. > > The gates are driven with a toroidal transformer and the whole > circuit is just a scaled up version of my original TX, which works fine. > It generates healthy power into a 50 ohm dummy load but on > connection to the aerial circuit - bang ! > The aerial system is identical to that used with the old TX ! > > Has anyone any ideas on what's causing the problem and how to cure > it ? > > I'm running out of FET's and my nerves are somewhat frayed (shell > shock!) > > 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 >