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From: "Markus Vester" <markusvester@aol.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4D22026B.7070908@iup.uni-heidelberg.de>
Date: Tue, 4 Jan 2011 00:00:53 +0100
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Subject: Re: VLF: DK7FC's "big" VLF PA - Outphasing
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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

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	charset="ISO-8859-15"
Content-Transfer-Encoding: quoted-printable

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3Dtext/html;charset=3Diso-8859=
-15>
<META content=3D"MSHTML 6.00.6000.17093" name=3DGENERATOR></HEAD>
<BODY id=3DMailContainerBody   style=3D"PADDING-RIGHT: 10px; PADDING-L=
EFT: 10px; PADDING-TOP: 15px" text=3D#000000   bgColor=3D#ffffff leftM=
argin=3D0 topMargin=3D0 CanvasTabStop=3D"true"   name=3D"Compose messa=
ge area">
<DIV><FONT face=3DArial size=3D2>Dear Stefan, </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>thanks very much for sharing this ver=
y useful=20
design!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Just in case you would like to extend=
 this&nbsp;to=20
linear modulation: </FONT><FONT face=3DArial size=3D2>The H-bridge top=
ology=20
naturally lends itself to the Outphasing technique (aka "Chireix" modu=
lation",=20
"Ampliphase", "LINC"),&nbsp;which was invented&nbsp;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:&nbsp;180=B0&nbsp;gives full power,=
 90=B0 gives -3=20
dB, and 0=B0 gives no differential output across the load.</FONT></DIV=
>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Instead of&nbsp;generating the two ca=
rriers&nbsp;by=20
special&nbsp;envelope-driven phaseshifter hardware, you could=20
also&nbsp;take&nbsp;a software approach through the two outputs of a=
 stereo=20
soundcard. I</FONT><FONT face=3DArial size=3D2>t may then be best to=
 feed the PA=20
drivers directly, avoiding the dividers&nbsp;which&nbsp;can<FONT face=
=3DArial   size=3D2> introduce an unwanted&nbsp;180=B0 ambiguity.</FON=
T></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>If you feel like trying this concept,=
 I could be=20
persuaded to adapt the Chirped Hell software for this purpose. What da=
y&nbsp;is=20
your birthday? ;-))</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Best regards,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Markus (DF6NM)</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>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!&nbsp;</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV></BODY></HTML>

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