Return-Path: Received: from rly-dc05.mx.aol.com (rly-dc05.mail.aol.com [172.19.136.34]) by air-dc09.mail.aol.com (v120.9) with ESMTP id MAILINDC092-b1d472f123b163; Mon, 05 Nov 2007 07:53:24 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-dc05.mx.aol.com (v120.9) with ESMTP id MAILRELAYINDC051-b1d472f123b163; Mon, 05 Nov 2007 07:53:17 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Ip1Rs-0007BO-7K for rs_out_1@blacksheep.org; Mon, 05 Nov 2007 12:53:00 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Ip1Rr-0007BF-M4 for rsgb_lf_group@blacksheep.org; Mon, 05 Nov 2007 12:52:59 +0000 Received: from smtp3.wanadoo.co.uk ([193.252.22.156] helo=smtp3.freeserve.com) by relay2.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Ip1Ro-00022g-Jv for rsgb_lf_group@blacksheep.org; Mon, 05 Nov 2007 12:52:59 +0000 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3207.me.freeserve.com (SMTP Server) with ESMTP id DF6AF9000043 for ; Mon, 5 Nov 2007 13:52:50 +0100 (CET) Received: from AGB (unknown [91.109.52.228]) by mwinf3207.me.freeserve.com (SMTP Server) with SMTP id 9A55B900008E for ; Mon, 5 Nov 2007 13:52:50 +0100 (CET) X-ME-UUID: 20071105125250632.9A55B900008E@mwinf3207.me.freeserve.com Message-ID: <003601c81faa$d39e08b0$0d00000a@AGB> From: "Graham" To: References: <007301c81fa0$aabd9a00$65ebfc3e@g3kev> <20071105121359.09bfb671@saluki.ngw.uk.com> Date: Mon, 5 Nov 2007 12:53:02 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3198 X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=disabled,AWL=0.089 Subject: Re: LF: CLASS D E.... Instrumet induced errors ? Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=original Content-Transfer-Encoding: quoted-printable 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-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: listenair ; SPF_helo : X-AOL-SCOLL-AUTHENTICATION: listenair ; SPF_822_from : ..... The 'I' supply to the stage dosent look like a sine wave , more like=20 a pulse train ? , thats the case will need a little more than a avo-8 to=20 get the correct value, vlaues may be actually higher than conventionally=20 measured, giving lower conversion factors ? supply bandwith may also be a=20 issure, caused by switching -rise times- is there a voltage collapse on the= =20 leading edge, there must be some , but how much , reducing the 'area under= =20 the curve' ? G .. ----- Original Message -----=20 From: "John GM4SLV" To: Sent: Monday, November 05, 2007 12:13 PM Subject: Re: LF: CLASS D E On Mon, 5 Nov 2007 11:39:54 -0000 "hamilton mal" wrote: > Hi all > Tnx to all for the information, but some of the figures do not work > out. How are the % figures measured. > One simple method is to calculate the DC input PWR in watts (I x V) > then using an RF current meter calculate the PWR out (Isq x R) let R > be the norm 50 ohm D/load. Compare the two figures and calculate the > Eff % 73 de Mal/G3KEV > > > Again...with my TX At 50W output :- Dc supply =3D 18.7v at 3.4A Efficiency =3D 78% The math's is trivial..... 18.7V x 3.4A =3D 63.58W DC input 50W RF output (as measured on a homebrew power meter calibrated against a =C2=A320,000 R&S Spectrum analyser and precision 40dB power attenuator) Efficiency =3D Power Out / Power In 50 / 63.58 =3D 0.786 Hence 78.6% efficient. Of course if you can't accurately measure any of the necessary quantities then the end result will be meaningless. Measuring RF output using an RF ammeter and 50 ohm load is all well and good...but...how accurate is your RF ammeter? How accurate is the 50 ohms. How is the 50 ohms measured... at DC? Is it the same at RF? With a good Class-E amp and 90% efficiency it only takes one of your measurements to be out by a few percent to make the efficiency calculated to be really way out. Say (plucked out of thin air example):- DC input (most accurately measured parameters?) 13.8V at 5.3A =3D 73.14W RF output as measured by your RF ammeter/50 ohm load 1.17A in 50 ohms =3D 68.4W Efficiency =3D 93.6% If your RF ammeter reads 5% high... I =3D 1.23A in 50 ohms =3D 75W Out Efficiency =3D 103% Contact the Nobel Prize Committee... you've invented the prepetual motion machine..... If your 50 ohm load is really 49 ohms however... 1.17A in 49 ohms =3D 67W Efficiency =3D 91.7% Don't assume there's some black magic mumbo-jumbo Emperor's New Clothes syndrome with MOSFET amps just because it appears that you can't tie down a reliable efficiency figure. Little errors make big differences. The important thing is that they work, don't get hot and can produce serious power for little engineering. Try getting a 2N3055 to produce 150W on 500kHz. Cheers, John --=20 No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.5.503 / Virus Database: 269.15.19/1106 - Release Date: 11/2/2007=20 21:46