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Date: Sun, 29 Dec 2013 09:12:19 +0100
From: wolf_dl4yhf <dl4yhf@freenet.de>
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Subject: Re: LF: VLF exciter
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My suggestion:

Use two outputs from the stereo soundcard:
An "amplitude" and a "phase" channel. The output from the phase channel 
will be a square wave, coherent, constant amplitude, fed to the divider 
chain. The "amplitude" channel delivers, well, the amplitude (as a 
waveform with variable voltage) which, after rectification, drives the 
final voltage via an additional mosfet. I think the software option is 
already there, and iirc it has been used (by Jim ?) for an LF PA.
This way, you could even use amplitude shaping if the bandwidth (from 
the hard-keyed PA) was a problem - which I don't think it is, on VLF.

Cheers,
   Wolf

  (p.s. problem with the "very long command lines" already fixed, new SL 
version will be uploaded soon).

Am 29.12.2013 02:43, schrieb Stefan Schäfer:
>
> Am 28.12.2013 23:33, schrieb Markus Vester:
>> [...]
>> PS Any progress on bypassing the divider in your VLF transmit chain?
>
> Aaah, no, i forgot that. So i cannot transmit OP32 on VLF because it 
> would be incoherent then. So i have to key the PA via a VOX and OP32 
> tones, still :-/
>
> In this H bridge PA config, an exact 50% duty cycle isn't needed, so i 
> may actually remove the divider. But then i need a solid and defined 
> input signal wave form! How do i get an inverted signal then? A 
> transformer isn't possible since i like to have a wide frequency range 
> of the PA. So far it works from 10 Hz to > 100 kHz. With the frequency 
> divider, the wave form can be quite distorted, no problem unless the 
> peak reaches the necessary voltage level. So maybe it is better to 
> build the VOX circuit instead? Also i want to leave the PA circuit as 
> it is, for nostalgic reasons :-)
> Or do you have another idea? I remember that circuit with the XOR gates...
>
> 73, Stefan/DK7FC


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    <div class="moz-cite-prefix">My suggestion:<br>
      <br>
      Use two outputs from the stereo soundcard: <br>
      An "amplitude" and a "phase" channel. The output from the phase
      channel will be a square wave, coherent, constant amplitude, fed
      to the divider chain. The "amplitude" channel delivers, well, the
      amplitude (as a waveform with variable voltage) which, after
      rectification, drives the final voltage via an additional mosfet.
      I think the software option is already there, and iirc it has been
      used (by Jim ?) for an LF PA.<br>
      This way, you could even use amplitude shaping if the bandwidth
      (from the hard-keyed PA) was a problem - which I don't think it
      is, on VLF.<br>
      <br>
      Cheers,<br>
      &nbsp; Wolf <br>
      <br>
      &nbsp;(p.s. problem with the "very long command lines" already fixed,
      new SL version will be uploaded soon).<br>
      <br>
      Am 29.12.2013 02:43, schrieb Stefan Sch&auml;fer:<br>
    </div>
    <blockquote cite="mid:52BF7E2A.9000002@iup.uni-heidelberg.de"
      type="cite">
      <meta content="text/html; charset=ISO-8859-1"
        http-equiv="Content-Type">
      <br>
      Am 28.12.2013 23:33, schrieb Markus Vester:
      <blockquote cite="mid:DDBCC8F2ADC5452C85E1D13889D0C423@White"
        type="cite">
        <meta content="text/html; charset=ISO-8859-1"
          http-equiv="Content-Type">
        <meta name="GENERATOR" content="MSHTML 8.00.6001.23543">
        <font size="2"><font face="Arial">[...]</font></font>
        <div>&nbsp;</div>
        <div><font face="Arial" size="2">PS Any progress on bypassing
            the
            divider in your VLF transmit chain?</font></div>
      </blockquote>
      <font size="2"><font face="Arial"><br>
          Aaah, no, i forgot that. So i cannot transmit OP32 on VLF
          because it
          would be incoherent then. So i have to key the PA via a VOX
          and OP32
          tones, still :-/<br>
          <br>
          In this H bridge PA config, an exact 50% duty cycle isn't
          needed, so i
          may actually remove the divider. But then i need a solid and
          defined
          input signal wave form! How do i get an inverted signal then?
          A
          transformer isn't possible since i like to have a wide
          frequency range
          of the PA. So far it works from 10 Hz to &gt; 100 kHz. With
          the
          frequency divider, the wave form can be quite distorted, no
          problem
          unless the peak reaches the necessary voltage level. So maybe
          it is
          better to build the VOX circuit instead? Also i want to leave
          the PA
          circuit as it is, for nostalgic reasons :-)<br>
          Or do you have another idea? I remember that circuit with the
          XOR
          gates...<br>
          <br>
          73, Stefan/DK7FC<br>
        </font></font>
    </blockquote>
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