Return-Path: Received: from mtain-mc08.r1000.mx.aol.com (mtain-mc08.r1000.mx.aol.com [172.29.96.80]) by air-da06.mail.aol.com (v129.4) with ESMTP id MAILINDA064-86664d2c8867b5; Tue, 11 Jan 2011 11:42:15 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mc08.r1000.mx.aol.com (Internet Inbound) with ESMTP id 3319A380000B6; Tue, 11 Jan 2011 11:42:13 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PchH7-0001SD-5I for rs_out_1@blacksheep.org; Tue, 11 Jan 2011 16:40:49 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PchH5-0001S4-I3 for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2011 16:40:47 +0000 Received: from out1.ip05ir2.opaltelecom.net ([62.24.128.241]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PchH2-0000eR-ID for rsgb_lf_group@blacksheep.org; Tue, 11 Jan 2011 16:40:47 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AisFAHMWLE1Ok89J/2dsb2JhbACSEQOSJHO8XYVMBIFfjGmCXA X-IronPort-AV: E=Sophos;i="4.60,307,1291593600"; d="scan'208,217";a="328292605" Received: from unknown (HELO xphd97xgq27nyf) ([78.147.207.73]) by out1.ip05ir2.opaltelecom.net with SMTP; 11 Jan 2011 16:40:37 +0000 Message-ID: <005d01cbb1ae$439d76d0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: Date: Tue, 11 Jan 2011 16:40:32 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: First 500kHz Class E breadboard Content-Type: multipart/alternative; boundary="----=_NextPart_000_005A_01CBB1AE.434089C0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE 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: 3039ac1d60504d2c886527c7 X-AOL-IP: 195.171.43.25 ------=_NextPart_000_005A_01CBB1AE.434089C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable An 80% efficient class E amp that cost nothing for parts cannot be bad= . Mine also went first time with the calculated values and has been goin= g strong ever since on 500 Kcs All the bits came from my junk box or off old cct boards inc fets To buy an amplifier capable of running several hundred watts would cos= t a fortune. de g3kev ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, January 11, 2011 2:49 PM Subject: LF: First 500kHz Class E breadboard OK. The first attempt at a Class E PA using all junk box bits has= been a bit more sucessful as reasonably expected, and has flagged up= exactly what several people did mention on this reflector. Using= a the somewhat old and vernerable IRF462 with its Rdson of 0.4 ohms,= even with two in parallel, the efficiency achieved never exceeded 84%= , and looking at the scope trace the voltage drop across them at peak= was in the region of 7 - 9V. So its clear where the power was being= lost. =20 All the caps were made up from parallel combinations of the 3.3nF th= ings I had so many of - and knowing the right scope trace shape to tun= e for made setting up straightforward. The lower efficiency meant th= e 500 Watts aim couldn't be achieved, but at a 50V rail I did get a= smidgen more than 410W, and felt this is about the limit I really oug= ht to go for with this sub-optimum choice of device The additional losses in the FETs made tuning flatter than expected,= and there were several combinations of Caps (all with the same fixed= L) that gave a similar overall efficiency once the trace had been opt= imised, Just max power was different. The total cost in real money spent on components used in the final= breadboard was absolutely zero, everything came from the junk box. = (Although the 3.3nF capactors were all originally bought new back in= 1997 when I was resonanting a 3m diameter two turn loop of water pip= e on 73kHz) I'll do a write up and post on my web site for anyone who wants to= build similar PAs.. There are a couple of minor gotchas its worth lo= oking out for - not least burnt fingers on an inadequate DC feed torro= id. Now I know the desgn is so easy to get going, may spend a bit of mon= ey on some more modern devices and aim for a better efficiency.=20 Andy www.g4jnt.com ------=_NextPart_000_005A_01CBB1AE.434089C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
An 80% efficient class E amp that cos= t nothing for=20 parts cannot be bad.
Mine also went first time with the ca= lculated=20 values and has been going strong ever since on 500 Kcs
All the bits came from my junk= box or off old=20 cct boards inc fets
To buy an amplifier capable of runnin= g several=20 hundred watts would cost a fortune.
de g3kev
 
 
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Tuesday, January 11, 20= 11 2:49=20 PM
Subject: LF: First 500kHz Cla= ss E=20 breadboard

OK.  The first attempt at a Class E PA using all junk box= bits=20 has been a bit more sucessful as reasonably expected,= and has=20 flagged up exactly what several people did mention on this=20 reflector.    Using a the somewhat old and=20 vernerable IRF462 with its Rdson of 0.4 ohms, even with two in= parallel,=20 the efficiency achieved never exceeded 84%, and looking at the scope= trace the=20 voltage drop across them at peak was in the region of 7 - 9V. &= nbsp; So=20 its clear where the power was being lost.   
 
All the caps were made up from parallel combinations of the 3.3= nF things=20 I had so many of - and knowing the right scope trace shape to tune= for made=20 setting up straightforward.   The lower efficiency meant= the 500=20 Watts aim couldn't be achieved,  but at a 50V rail I= did get a=20 smidgen more than 410W, and felt this is about the limit I really ou= ght to go=20 for with this sub-optimum choice of device
 
The additional losses in the FETs made tuning flatter than= expected,=20 and there were several combinations of Caps (all with the same&= nbsp;fixed=20 L) that gave a similar overall efficiency once the trace had be= en=20 optimised, Just max power was different.
 
The total cost in real money spent on components used in the fi= nal=20 breadboard was absolutely zero, everything came from the junk= box. =20 (Although the 3.3nF capactors were all originally bought new back in= 1997 when=20 I was resonanting a 3m diameter two turn  loop of water pipe on= =20 73kHz)
 
I'll do a write up and post on my web site for anyone who wants= to build=20 similar PAs..  There are a couple of minor gotchas its worth lo= oking out=20 for - not least burnt fingers on an inadequate DC feed torroid.
 
Now I know the desgn is so easy to get going, may spend a bit= of money on=20 some more modern devices and aim for a better efficiency. 
 
Andy
 
------=_NextPart_000_005A_01CBB1AE.434089C0--