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References: <a980b527-8405-6a80-bb68-2c16dfd191f6@kabelmail.de>
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From: David Bowman <davidg0mrf@gmail.com>
Date: Mon, 8 Oct 2018 21:05:33 +0000
Message-ID: <CA+GfORtOqwOqTJOwDPQnM7acjw1k5rWqBAPKiYq=DaFrd0m7FA@mail.gmail.com>
Subject: Re: LF: Class E PA
To: rsgb_lf_group@blacksheep.org
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Hi Tom.

If it helps, I believe nearly all broadcast transmitters keep the drive
running and then key the supply to the many paralleled FETs in the PA.
Of course, that also is a neat way of applying AM as pulse width
modulation......but I'm sure it will be fine for your system of modulation
too.

73

David

On Sun, Oct 7, 2018 at 5:52 PM DK1IS <DK1IS@kabelmail.de> wrote:

> Hello Group,
>
> Planning a new single-ended Class E PA for my activities on the Dreamers
> Band (8.27 kHz) two questions came up - perhaps someone can help me:
> -  Being interested only in on-off-keying I=C2=B4m concerned about the
> capacitor in parallel to the power FET which in my case on VLF will be in
> the uF range. If the DC supply is on and without gate drive this capacito=
r
> is charged to the DC supply voltage. At the first positive gate pulse it
> discharges via the drain-source-path, the current being  limited only by
> parasitc impedances - a poorly defined condition which usually has to be
> avoided. Does this mean that I have to apply drive continously and key th=
e
> DC power supply only, perhaps synchronously to the next positive drive
> pulse?
>
> -  Is there any rule of thumb for the inductance of the rf choke in the
> drain-power supply path?
>
> Thanks for any idea!
>
> 73,
> Tom, DK1IS
> www.qrz.com/db/dk1is
>

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<div dir=3D"ltr"><div>Hi Tom.</div><div><br></div><div>If it helps, I belie=
ve nearly all broadcast transmitters keep the drive running and then key th=
e supply to the many paralleled FETs in the PA.</div><div>Of course, that a=
lso is a neat way of applying AM as pulse width modulation......but I&#39;m=
 sure it will be fine for your system of modulation too.</div><div><br></di=
v><div>73</div><div><br></div><div>David<br></div></div><br><div class=3D"g=
mail_quote"><div dir=3D"ltr">On Sun, Oct 7, 2018 at 5:52 PM DK1IS &lt;<a hr=
ef=3D"mailto:DK1IS@kabelmail.de">DK1IS@kabelmail.de</a>&gt; wrote:<br></div=
><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1=
px #ccc solid;padding-left:1ex">
 =20

   =20
 =20
  <div text=3D"#000000" bgcolor=3D"#FFFFFF">
    <p></p>
    <p>
      <p class=3D"MsoNormal"><span lang=3D"EN-US">Hello
          Group,</span></p>
      <p class=3D"MsoNormal"><span lang=3D"EN-US">Planning a new
          single-ended Class E PA for my activities on the Dreamers Band
          (8.27 kHz) two
          questions came up - perhaps someone can help me:</span></p>
    </p>
    <span style=3D"font-family:Symbol" lang=3D"EN-US"><span><span style=3D"=
font:7.0pt &quot;Times New Roman&quot;"></span></span></span><span lang=3D"=
EN-US">-=C2=A0 Being
      interested only in on-off-keying I=C2=B4m concerned about the capacit=
or
      in parallel
      to the power FET which in my case on VLF will be in the uF range.
      If the DC
      supply is on and without gate drive this capacitor is charged to
      the DC supply
      voltage. At the first positive gate pulse it discharges via the
      drain-source-path,
      the current being <span>=C2=A0</span>limited
      only by
      parasitc impedances - a poorly defined condition which usually has
      to be
      avoided. Does this mean that I have to apply drive continously and
      key the DC
      power supply only, perhaps synchronously to the next positive
      drive pulse?</span><br>
    =C2=A0
    <span style=3D"font-family:Symbol" lang=3D"EN-US"><span><br>
        -=C2=A0 <span style=3D"font:7.0pt &quot;Times New Roman&quot;"></sp=
an></span></span><span lang=3D"EN-US">Is
      there any rule of thumb for the inductance of the rf choke in the
      drain-power
      supply path?</span>
    <p>
      <p class=3D"MsoNormal"><span lang=3D"EN-US">Thanks for
          any idea!</span></p>
      <p class=3D"MsoNormal"><span lang=3D"EN-US">73,<br>
          Tom, DK1IS<br>
          <a class=3D"m_-3004232056685750992moz-txt-link-abbreviated" href=
=3D"http://www.qrz.com/db/dk1is" target=3D"_blank">www.qrz.com/db/dk1is</a>=
<br>
        </span></p>
    </p>
  </div>

</blockquote></div>

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