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Date: Sun, 29 Dec 2013 17:02:05 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: VLF exciter
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Hi Markus,

Thanks for the ideas. Well, the PA needs and has a separate PTT input 
anyway, for flexibility reasons. So i may just use the VOX circuit.

73, Stefan

Am 29.12.2013 11:33, schrieb Markus Vester:
> Hi Stefan,
> here's a quick sketch of how I would go about it. You wanted XORs so 
> here's one with XORs ;-) But in this circuit they serve basically only 
> as inverting or noninverting opamps, depending whether their other 
> input is connected to the (+) supply or (-) ground.
> The top left part tries to pull the duty cycle close to 50%. The AC 
> voltage is reduced, and with the negative DC feedback the comparator 
> threshold settles to a point where the avaerage output is at half 
> supply voltage (eg 2.5V). BTW this is the opposite function to the 
> "duty cycle amplifier" which I use in my automatic LF variometer 
> df6nm.bplaced.net/LF/pictures/AutoTuner.zip 
> <http://df6nm.bplaced.net/LF/pictures/AutoTuner.zip> .
> The output circuit is an inverter used for inverting one of the drives 
> ;-) The pair of XORs should equalize the gate delay.
> The vox circuit at the bottom with the rectifier is straightforward, 
> including a bit of hysteresis introduced by positive feedback.
> Best 73,
> Markus (DF6NM)
>

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Hi Markus, <br>
<br>
Thanks for the ideas. Well, the PA needs and has a separate PTT input
anyway, for flexibility reasons. So i may just use the VOX circuit.<br>
<br>
73, Stefan<br>
<br>
Am 29.12.2013 11:33, schrieb Markus Vester:
<blockquote cite="mid:C521886643E245A293777EEEB9B4A325@White"
 type="cite">
  <meta content="text/html; charset=ISO-8859-1"
 http-equiv="Content-Type">
  <meta name="GENERATOR" content="MSHTML 8.00.6001.23543">
  <div><font face="Arial" size="2">Hi Stefan,</font></div>
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">here's a quick sketch of how I would
go about it. You wanted XORs so here's one with XORs ;-) But in this
circuit they serve basically only as inverting or noninverting opamps,
depending whether their other input is connected to the (+) supply or
(-) ground.</font></div>
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">The top left part tries to pull the
duty cycle close to 50%. The&nbsp;AC voltage is reduced, and with&nbsp;the
negative DC feedback the&nbsp;comparator threshold settles to a point where
the avaerage output is at&nbsp;half supply&nbsp;voltage (eg 2.5V). BTW this is
the opposite function to&nbsp;the "duty cycle amplifier" which I use in
my&nbsp;automatic LF variometer </font><font face="Arial" size="2"><a
 moz-do-not-send="true"
 title="http://df6nm.bplaced.net/LF/pictures/AutoTuner.zip
STRG + Klicken, um Verkn&uuml;pfung zu folgen"
 href="http://df6nm.bplaced.net/LF/pictures/AutoTuner.zip">df6nm.bplaced.net/LF/pictures/AutoTuner.zip</a>&nbsp;.</font></div>
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">The output circuit is an inverter
used for inverting one of the drives ;-)&nbsp;The pair of XORs&nbsp;should
equalize the gate delay.</font></div>
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">The&nbsp;vox circuit&nbsp;at the bottom with
the rectifier is straightforward, including&nbsp;a bit of hysteresis
introduced by positive feedback.&nbsp;&nbsp;&nbsp;</font></div>
  <div>&nbsp;</div>
  <div><font face="Arial" size="2">Best 73,</font></div>
  <div><font face="Arial" size="2">Markus (DF6NM)</font></div>
  <br>
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