Message-ID: <4D23693E.3080009@freenet.de>
Date: Tue, 04 Jan 2011 19:38:54 +0100
From: wolf_dl4yhf <dl4yhf@freenet.de>
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Subject: Re: VLF: DK7FC's "big" VLF PA - Outphasing
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Hello Markus and Stefan,

Phew, that sounds interesting.. the question is how to convert the=20
output of the inverse FFT (with the 'analog' chirped Hell signal) into=20
your described digital (square wave) output signal. Could it be easier=20
to synthesize this signal directly, i.e. without an FFT at all ?

Cheers,
   Wolf  DL4YHF .

Am 04.01.2011 00:00, schrieb Markus Vester:
> Dear Stefan,
> thanks very much for sharing this very useful design!
> Just in case you would like to extend this to linear modulation: The=20
> H-bridge topology naturally lends itself to the Outphasing technique=20
> (aka "Chireix" modulation", "Ampliphase", "LINC"), which was=20
> invented in the 1930ies to increase AM transmitter efficiency. The=20
> idea is to drive the two half-bridges separately with a variable phase=
=20
> difference: 180=B0 gives full power, 90=B0 gives -3 dB, and 0=B0 gives=
 no=20
> differential output across the load.
> Instead of generating the two carriers by special envelope-driven=20
> phaseshifter hardware, you could also take a software approach through=
=20
> the two outputs of a stereo soundcard. It may then be best to feed the=
=20
> PA drivers directly, avoiding the dividers which canintroduce an=20
> unwanted 180=B0 ambiguity.
> If you feel like trying this concept, I could be persuaded to adapt=20
> the Chirped Hell software for this purpose. What day is your birthday?=
=20
> ;-))
> Best regards,
> Markus (DF6NM)
> PS: In case you decide to use small audio transformers at the input,=20
> make sure their insulation can safely withstand the line voltage!

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    <meta content=3D"text/html; charset=3DISO-8859-15"        http-equiv=
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    Hello Markus and Stefan,<br>
    <br>
    Phew, that sounds interesting.. the question is how to convert the
    output of the inverse FFT (with the 'analog' chirped Hell signal)
    into your described digital (square wave) output signal. Could it be
    easier to synthesize this signal directly, i.e. without an FFT at
    all ?<br>
    <br>
    Cheers,<br>
    =A0 Wolf=A0 DL4YHF .<br>
    <br>
    Am 04.01.2011 00:00, schrieb Markus Vester:
    <blockquote cite=3D"mid:A4FCBFE8D0434967960A11F60799422D@White"     =
   type=3D"cite">
      <meta http-equiv=3D"Content-Type" content=3D"text/html;          cha=
rset=3DISO-8859-15">
      <meta content=3D"MSHTML 6.00.6000.17093" name=3D"GENERATOR">
      <div><font face=3D"Arial" size=3D"2">Dear Stefan, </font></div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">thanks very much for sharing th=
is
          very useful design!</font></div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">Just in case you would like to
          extend this=A0to linear modulation: </font><font face=3D"Arial"=
            size=3D"2">The H-bridge topology naturally lends itself to the
          Outphasing technique (aka "Chireix" modulation", "Ampliphase",
          "LINC"),=A0which was invented=A0in the 1930ies to increase AM
          transmitter efficiency. The idea is to drive the two
          half-bridges separately with a variable phase
          difference:=A0180=B0=A0gives full power, 90=B0 gives -3 dB, and=
 0=B0
          gives no differential output across the load.</font></div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">Instead of=A0generating the two
          carriers=A0by special=A0envelope-driven phaseshifter hardware,=
 you
          could also=A0take=A0a software approach through the two outputs=
 of
          a stereo soundcard. I</font><font face=3D"Arial" size=3D"2">t ma=
y
          then be best to feed the PA drivers directly, avoiding the
          dividers=A0which=A0can<font face=3D"Arial" size=3D"2"> introduce=
 an
            unwanted=A0180=B0 ambiguity.</font></font></div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">If you feel like trying this
          concept, I could be persuaded to adapt the Chirped Hell
          software for this purpose. What day=A0is your birthday? ;-))</fo=
nt></div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">Best regards,</font></div>
      <div><font face=3D"Arial" size=3D"2">Markus (DF6NM)</font></div>
      <div>=A0</div>
      <div>=A0</div>
      <div><font face=3D"Arial" size=3D"2">PS: In case you decide to use
          small audio transformers at the input, make sure their
          insulation can safely withstand the line voltage!=A0</font></div=
>
      <div>=A0</div>
    </blockquote>
    <br>
  </body>
</html>

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