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The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Hi Eike, you are right, the drain voltage waveform is not perfect! I have since corrected the duty cycle on the gate to be exactly 50%. I have also added two 200 V zener diodes from the drain to the source. This will clamp the voltage to 400 V which is quite safe for a 500 V FET. The zener diodes together with the fuses, I think, make this design pretty bullet proof. [...] Content analysis details: (-0.7 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.210.169 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (dtsifakis[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: ac0f6ff1af52b6036ac1f4fe0c2bd52c Subject: Re: Re: LF: My transmit converter description Content-Type: text/plain; charset=ISO-8859-1 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-SCOLL-AUTHENTICATION: mtain-mk05.r1000.mx.aol.com ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1d61895110d1262bb0 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none Hi Eike, you are right, the drain voltage waveform is not perfect! I have since corrected the duty cycle on the gate to be exactly 50%. I have also added two 200 V zener diodes from the drain to the source. This will clamp the voltage to 400 V which is quite safe for a 500 V FET. The zener diodes together with the fuses, I think, make this design pretty bullet proof. 73, Dimitris PS Nothing wrong with your english :-) 2013/2/5 Eike Katzera : > Hi Dimitros, > the pulse shape in this picture does not look good: > http://people.physics.anu.edu.au/~dxt103/472/nltt/vk1sv-drain.jpg > The reason seams to be the duty cycle at the gate. Please try to change R5 > to a 100k potentiometer and trim it to a clean single Pilse an the drain. I > solved the same problem tha way in my PA, wich killed my IRF540. > Kind regards > Eike DL3IKE > PS: sorry for my english ;) > Gesendet: Dienstag, 05. Februar 2013 um 08:45 Uhr > Von: "Victor van Kooten" > An: rsgb_lf_group@blacksheep.org > Betreff: Re: LF: My transmit converter description > Looks very nice Dimitris,hope to see/hear you soon, > > 73 > > Victor > >>>> Dimitrios Tsifakis 05/02/2013 01:50 >>> > Hello group, > > My transmit converter is now finished and tested - it survived two > sessions of 50% duty cycle WSPR transmissions on 475 kHz and the > results are great. I thought others may find this useful, so I have > put a write-up on my web page: > > http://people.physics.anu.edu.au/~dxt103/472/nltt/ > > It is a 50 W class-e PA designed for 50 ohm impedance, so there is no > need for an impedance transformer. Doesn't get simpler than that :-) > The driving circuit is based on G3XBM Roger's design with the > difference of a 10 MHz OCXO LO and the addition of a beefy MOSFET > driver. > > 73, Dimitris VK1SV > > > >