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From: Roland Bruestle <r@mbsks.franken.de>
Message-ID: <571CFAD6.8000806@mbsks.franken.de>
Date: Sun, 24 Apr 2016 18:56:54 +0200
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Subject: Re: LF: TXing on VLF again, my first homemade linear PA! :-)
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Hello,
I'm on 8270Hz with 0.3A as test transmission.  I hope our signal 
separation is good enough.
Roland Dl3NDR

Am 23.04.2016 um 18:51 schrieb DK7FC:
> Hi all,
>
> Since about 16 UTC i'm transmitting on 8270.00500 Hz again. The 
> antenna current is about 200 mA. It is a first test over a longer time 
> with my new PA.
>
> I have been off the air for a few days now becuase i destroyed my 
> audio amp that i used as a VLF PA. Somehow i started to like the idea 
> of a clean sine wave coming from the PA. Low pass filters are hard to 
> design for VLF, you know. Since i don't like buying and since i didn't 
> find another one in the trash, i 'had to' (actually /wanted/) to build 
> my own. It is a class-AB PA now running at 20V DC using 2x IRFP064N 
> against ground. Opposite phase drive signals are generated by a small 
> blue ferrite core with 20 quadfilar turns. On the primary side, 2 of 
> these 4 windings are in series. On the scope, the signal looks quite 
> good. The 3rd harmonic is at about -20 dBc, certainly improvable. But 
> it's just version 0.2 now ;-)
> A large ferrite core is used to up-transform the voltage to about 220V 
> rms for this power level (i'm not spot on the resonance), also 
> providing galvanic decoupling.
>
> A photo can be found at
> https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg
> https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg
>
> The PA consumes 3.6A at 20V DC now. Improvements will follow...
>
> The signal will stay on air for a few hours now.
>
> 73, Stefan


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    <div class="moz-cite-prefix">Hello,<br>
      I'm on 8270Hz with 0.3A as test transmission.  I hope our signal
      separation is good enough.<br>
      Roland Dl3NDR<br>
      <br>
      Am 23.04.2016 um 18:51 schrieb DK7FC:<br>
    </div>
    <blockquote cite="mid:571BA7FE.6080601@posteo.de" type="cite">
      <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
      Hi all, <br>
      <br>
      Since about 16 UTC i'm transmitting on 8270.00500 Hz again. The
      antenna
      current is about 200 mA. It is a first test over a longer time
      with my
      new PA.<br>
      <br>
      I have been off the air for a few days now becuase i destroyed my
      audio
      amp that i used as a VLF PA. Somehow i started to like the idea of
      a
      clean sine wave coming from the PA. Low pass filters are hard to
      design
      for VLF, you know. Since i don't like buying and since i didn't
      find
      another one in the trash, i 'had to' (actually <i>wanted</i>) to
      build
      my own. It is a class-AB PA now running at 20V DC using 2x
      IRFP064N
      against ground. Opposite phase drive signals are generated by a
      small
      blue ferrite core with 20 quadfilar turns. On the primary side, 2
      of
      these 4 windings are in series. On the scope, the signal looks
      quite
      good. The 3rd harmonic is at about -20 dBc, certainly improvable.
      But
      it's just version 0.2 now ;-) <br>
      A large ferrite core is used to up-transform the voltage to about
      220V
      rms for this power level (i'm not spot on the resonance), also
      providing galvanic decoupling.<br>
      <br>
      A photo can be found at <br>
      <a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg">https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg</a><br>
      <a moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg">https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg</a><br>
      <br>
      The PA consumes 3.6A at 20V DC now. Improvements will follow...<br>
      <br>
      The signal will stay on air for a few hours now.<br>
      <br>
      73, Stefan<br>
    </blockquote>
    <br>
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