Return-Path: Received: from mtain-dl11.r1000.mx.aol.com (mtain-dl11.r1000.mx.aol.com [172.29.74.217]) by air-dd05.mail.aol.com (v129.4) with ESMTP id MAILINDD051-860b4d225579280; Mon, 03 Jan 2011 18:02:17 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dl11.r1000.mx.aol.com (Internet Inbound) with ESMTP id 990BF380000CA; Mon, 3 Jan 2011 18:02:15 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PZtOk-0007ot-1b for rs_out_1@blacksheep.org; Mon, 03 Jan 2011 23:01:06 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PZtOj-0007ok-Ka for rsgb_lf_group@blacksheep.org; Mon, 03 Jan 2011 23:01:05 +0000 Received: from imr-da02.mx.aol.com ([205.188.105.144]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PZtOh-000813-LG for rsgb_lf_group@blacksheep.org; Mon, 03 Jan 2011 23:01:05 +0000 Received: from mtaout-mb03.r1000.mx.aol.com (mtaout-mb03.r1000.mx.aol.com [172.29.41.67]) by imr-da02.mx.aol.com (8.14.1/8.14.1) with ESMTP id p03N0qhY023096 for ; Mon, 3 Jan 2011 18:00:52 -0500 Received: from White (nrbg-4dbfb899.pool.mediaWays.net [77.191.184.153]) by mtaout-mb03.r1000.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id B26F5E00008C for ; Mon, 3 Jan 2011 18:00:49 -0500 (EST) Message-ID: From: "Markus Vester" To: References: <4D22026B.7070908@iup.uni-heidelberg.de> Date: Tue, 4 Jan 2011 00:00:53 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 X-MimeOLE: Produced By Microsoft MimeOLE V12.0.1606 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: VLF: DK7FC's "big" VLF PA - Outphasing Content-Type: multipart/alternative; boundary="----=_NextPart_000_0018_01CBABA2.747DE350" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_NAME 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: 3039ac1d4ad94d2255776446 X-AOL-IP: 195.171.43.25 ------=_NextPart_000_0018_01CBABA2.747DE350 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Dear Stefan,=20 thanks very much for sharing this very useful design! Just in case you would like to extend this to linear modulation: The= H-bridge topology naturally lends itself to the Outphasing technique= (aka "Chireix" modulation", "Ampliphase", "LINC"), which was invented= in the 1930ies to increase AM transmitter efficiency. The idea is to= drive the two half-bridges separately with a variable phase differenc= e: 180=B0 gives full power, 90=B0 gives -3 dB, and 0=B0 gives no diffe= rential output across the load. Instead of generating the two carriers by special envelope-driven phas= eshifter hardware, you could also take a software approach through the= two outputs of a stereo soundcard. It may then be best to feed the PA= drivers directly, avoiding the dividers which can introduce an unwant= ed 180=B0 ambiguity. If you feel like trying this concept, I could be persuaded to adapt th= e Chirped Hell software for this purpose. What day is your birthday?= ;-)) Best regards, Markus (DF6NM) PS: In case you decide to use small audio transformers at the input,= make sure their insulation can safely withstand the line voltage!=20 ------=_NextPart_000_0018_01CBABA2.747DE350 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Dear Stefan,
 
thanks very much for sharing this ver= y useful=20 design!
 
Just in case you would like to extend= this to=20 linear modulation: The H-bridge top= ology=20 naturally lends itself to the Outphasing technique (aka "Chireix" modu= lation",=20 "Ampliphase", "LINC"), which was invented in the 1930ies to= increase=20 AM transmitter efficiency. The idea is to drive the two half-bridges= separately=20 with a variable phase difference: 180=B0 gives full power,= 90=B0 gives -3=20 dB, and 0=B0 gives no differential output across the load.
 
Instead of generating the two ca= rriers by=20 special envelope-driven phaseshifter hardware, you could=20 also take a software approach through the two outputs of a= stereo=20 soundcard. It may then be best to= feed the PA=20 drivers directly, avoiding the dividers which can introduce an unwanted 180=B0 ambiguity.
 
If you feel like trying this concept,= I could be=20 persuaded to adapt the Chirped Hell software for this purpose. What da= y is=20 your birthday? ;-))
 
Best regards,
Markus (DF6NM)
 
 
PS: In case you decide to use small= audio=20 transformers at the input, make sure their insulation can safely withs= tand the=20 line voltage! 
 
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