Return-Path: Received: from rly-mg01.mx.aol.com (rly-mg01.mail.aol.com [172.20.83.107]) by air-mg01.mail.aol.com (v126.13) with ESMTP id MAILINMG014-9f14b4c62a9301; Tue, 12 Jan 2010 06:53:24 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-mg01.mx.aol.com (v125.7) with ESMTP id MAILRELAYINMG013-9f14b4c62a9301; Tue, 12 Jan 2010 06:53:15 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NUfI5-0000P8-1w for rs_out_1@blacksheep.org; Tue, 12 Jan 2010 11:52:05 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NUfI4-0000Oz-MT for rsgb_lf_group@blacksheep.org; Tue, 12 Jan 2010 11:52:04 +0000 Received: from pne-smtpout1-sn1.fre.skanova.net ([81.228.11.98]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NUfI1-0008LY-W4 for rsgb_lf_group@blacksheep.org; Tue, 12 Jan 2010 11:52:04 +0000 Received: from [127.0.0.1] (81.235.167.68) by pne-smtpout1-sn1.fre.skanova.net (7.3.140.3) (authenticated as u33233109) id 4AE169E6009D129A for rsgb_lf_group@blacksheep.org; Tue, 12 Jan 2010 12:51:56 +0100 Message-ID: <4B4C625C.4080501@telia.com> Date: Tue, 12 Jan 2010 12:51:56 +0100 From: "Johan H. Bodin" User-Agent: Thunderbird 2.0.0.23 (Windows/20090812) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <20100111090709.EAAFE31E706@smtps01.kuleuven.be> <4B4C1D36.3090707@telia.com> <38A51B74B884D74083D7950AD0DD85E82A1A94@File-Server-HST.hst.e-technik.tu-darmstadt.de> In-Reply-To: <38A51B74B884D74083D7950AD0DD85E82A1A94@File-Server-HST.hst.e-technik.tu-darmstadt.de> X-Karma: unknown: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: AW: LF: PA0 into Alaska 600m Content-Type: text/plain; charset=ISO-8859-1 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-Mailer: Unknown (No Version) Hi Stefan, yes, a single ended class E amplifier would give the same power with both FETs in parallel but, due to symmetry, the push-pull design has the advantage of cancelling all even order harmonics by design. 3f is the first harmonic to worry about so the lowpass filter can be made simpler. The added complexity of push-pull is minimal - one more capacitor and one more DC feeding choke. And, yes, an output transformer in case you didn't already use one for impedance matching in the single ended case. By the way, the amplitude of the first harmonics of a single ended class E amplifier (without lowpass filter!) is 0.51/QL (2f) and 0.08/QL (3f) with respect to the carrier (1f) amplitude. QL is the loaded Q of the series resonant tank, XL/Rload. Example: If QL =3D 5.1, a reasonable value, the amplitude of the 2f harmonic will be 0.51/5.1 =3D 0.1 compared to the carrier i.e. -20dBc. In a perfectly balanced push-pull circuit, the 2f harmonic will disappear so the first harmonic problem will be 3f at -36dBc which is "16dB easier" to filter and further from the carrier as well :-). 73 Johan SM6LKM ---- Stefan Sch=E4fer wrote: > Hi Johan,=20 > =20 > What are you planning? This sounds like QROO? Why using a push-pull clas= s E stage when a single stange can do it? > I am interested! :-) > =20 > Stefan/DK7FC