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From: DK1IS <DK1IS@kabelmail.de>
Message-ID: <42748aad-c73a-99a2-0406-3f8e0a59c579@kabelmail.de>
Date: Thu, 11 Oct 2018 15:33:30 +0200
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Subject: Re: LF: Class E PA
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Am 09.10.2018 um 19:20 schrieb DK7FC:
> Hi Tom,
>
> Why do you decide for a class-E at all? Do you see any actual=20
> advantage over a class D?
>
> 73, Stefan


Hi Stefan,

A very good question! Knowing you are a dedicated class D fan I have to=20
choose my words carefully ;-) ! - Well, I think class E would fit my=20
personal needs best:

  * single ended circuit, that means no timing problems at square wave
    drive with 50% duty cycle
  * no fiddling with dead times or double frequency drive
  * 28 V DC power supply is well sufficient for 180 W output bringing
    about 18 kV rms to my antenna at a current of 0.6 A (and that=C2=B4s =
the
    voltage limit of the antenna)
  * omission of all transformers between PA and the feeding point of the
    antenna: matching is part of the output network and so is the
    regular cable capacity
  * fine tuning can be done in the shack
  * perhaps even a little bit more efficiency than class D - but that=C2=B4=
s
    not so important

Meanwhile I found out that my nice commercial power supply (Ascom Frako,=20
24/26.8/28.2 V, 20 A, short-circuit proof, "unkaputtbar") has a control=20
input at logic level for a DC softstart with a time constant about 100=20
ms which won=C2=B4t affect the long lasting signals at vlf and avoids any=
 key=20
clicks. I=C2=B4ll use this input for keying thus omitting the problem wit=
h=20
the first positive gate pulse. Drive will be there all the time with=20
constant phase and asynchronous soft keying is done via the power supply.

73,
Tom, DK1IS
www.qrz.com/db/dk1is


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    <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Dutf=
-8">
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  <body text=3D"#000000" bgcolor=3D"#FFFFFF">
    <div class=3D"moz-cite-prefix">Am 09.10.2018 um 19:20 schrieb DK7FC:<=
br>
    </div>
    <blockquote type=3D"cite" cite=3D"mid:5BBCE35D.6050300@posteo.de">
      <meta content=3D"text/html; charset=3Dutf-8" http-equiv=3D"Content-=
Type">
      Hi Tom, <br>
      <br>
      Why do you decide for a class-E at all? Do you see any actual
      advantage
      over a class D?<br>
      <br>
      73, Stefan<br>
    </blockquote>
    <br>
    <br>
    Hi Stefan,<br>
    <br>
    A very good question! Knowing you are a dedicated class D fan I have
    to choose my words carefully ;-) ! - Well, I think class E would fit
    my personal needs best:<br>
    <ul>
      <li>single ended circuit, that means no timing problems at square
        wave drive with 50% duty cycle</li>
      <li>no fiddling with dead times or double frequency drive</li>
      <li>28 V DC power supply is well sufficient for 180 W output
        bringing about 18 kV rms to my antenna at a current of 0.6 A
        (and that=C2=B4s the voltage limit of the antenna)<br>
      </li>
      <li>omission of all transformers between PA and the feeding point
        of the antenna: matching is part of the output network and so is
        the regular cable capacity</li>
      <li>fine tuning can be done in the shack</li>
      <li>perhaps even a little bit more efficiency than class D - but
        that=C2=B4s not so important</li>
    </ul>
    <p>Meanwhile I found out that my nice commercial power supply (Ascom
      Frako, 24/26.8/28.2 V, 20 A, short-circuit proof, "unkaputtbar")
      has a control input at logic level for a DC softstart with a time
      constant about 100 ms which won=C2=B4t affect the long lasting sign=
als
      at vlf and avoids any key clicks. I=C2=B4ll use this input for keyi=
ng
      thus omitting the problem with the first positive gate pulse.
      Drive will be there all the time with constant phase and
      asynchronous soft keying is done via the power supply.</p>
    <p>73,<br>
      Tom, DK1IS<br>
      <a class=3D"moz-txt-link-abbreviated" href=3D"http://www.qrz.com/db=
/dk1is">www.qrz.com/db/dk1is</a><br>
    </p>
  </body>
</html>

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