To: rsgb_lf_group@blacksheep.org
From: DK1IS <DK1IS@kabelmail.de>
Message-ID: <e5dedb78-0cb5-e165-0475-e3bc599760fe@kabelmail.de>
Date: Sun, 14 Oct 2018 00:16:45 +0200
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.9.1
MIME-Version: 1.0
Subject: Re: VLF: Class E PA
Content-Type: multipart/alternative;
 boundary="------------D7518291A06D152F8375AFFA"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

This is a multi-part message in MIME format.
--------------D7518291A06D152F8375AFFA
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by smtp.kabelmail.de id w9DMDYkD031200

Hello group,

Just to close this thread:

Concerning the problem of the first drive pulse with DC power already=20
on: Bob, W1XP, made an important contribution in a private mail. He=20
pointed out that the current spike I was worried about would be limited=20
by the FETs output characteristic anyway. Looking to the data sheet of=20
my intended IRFB 4227 this seems to be true although there could persist=20
a certain limitation by the save operation area. Perhaps I was a little=20
bit too naive estimating the peak current as Vdc / Rdson ... Be that as=20
it may, using the newly discovered DC soft start feature of my power=20
supply should overcome this challenge. Controlled by a logic level input=20
it runs up the output voltage with a time constant of about 100 ms. This=20
will protect the FET, avoid any key clicks and won=C2=B4t affect the=20
readability of the long lasting vlf signals. To keep the signal phase=20
constant (essential on vlf) oscillator and gate drive of the FET won=C2=B4=
t=20
be keyed at all.

I=C2=B4ve just modified the antenna / loading coil system to resonate at =
8270=20
Hz without transformers, - 3dB band width now being 168 Hz. Including 25=20
m RG213U from the arbour to the shack (being later on part of the=20
matching network) the feeding impedance is now 480 Ohms pure resistive=20
which will be matched to the rest of the class E PA by its output=20
network. Thus I`m able to omit the two matching transformers being used=20
up to now, see www.qrz.com/db/dk1is <http://www.qrz.com/db/dk1is>.

Now I=C2=B4m waiting for the driver ICs coming from China - in Germany up=
 to=20
now without additional tax ;);-) !

Thanks for all the feedback, 73,
Tom, DK1IS


--------------D7518291A06D152F8375AFFA
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by smtp.kabelmail.de id w9DMDYkD031200

<html>
  <head>

    <meta http-equiv=3D"content-type" content=3D"text/html; charset=3Dutf=
-8">
  </head>
  <body text=3D"#000000" bgcolor=3D"#FFFFFF">
    <p>Hello group,</p>
    <p>Just to close this thread:<br>
      <br>
      Concerning the problem of the first drive pulse with DC power
      already on: Bob, W1XP, made an important contribution in a private
      mail. He pointed out that the current spike I was worried about
      would be limited by the FETs output characteristic anyway. Looking
      to the data sheet of my intended IRFB 4227 this seems to be true
      although there could persist a certain limitation by the save
      operation area. Perhaps I was a little bit too naive estimating
      the peak current as Vdc / Rdson ... Be that as it may, using the
      newly discovered DC soft start feature of my power supply should
      overcome this challenge. Controlled by a logic level input it runs
      up the output voltage with a time constant of about 100 ms. This
      will protect the FET, avoid any key clicks and won=C2=B4t affect th=
e
      readability of the long lasting vlf signals. To keep the signal
      phase constant (essential on vlf) oscillator and gate drive of the
      FET won=C2=B4t be keyed at all. <br>
      <br>
      I=C2=B4ve just modified the antenna / loading coil system to resona=
te
      at 8270 Hz without transformers, - 3dB band width now being 168
      Hz. Including 25 m RG213U from the arbour to the shack (being
      later on part of the matching network) the feeding impedance is
      now 480 Ohms pure resistive which will be matched to the rest of
      the class E PA by its output network. Thus I`m able to omit the
      two matching transformers being used up to now, see <a
        href=3D"http://www.qrz.com/db/dk1is" target=3D"_blank"
        class=3D"externalLink" rel=3D"nofollow">www.qrz.com/db/dk1is</a>.=
 <br>
      <br>
      Now I=C2=B4m waiting for the driver ICs coming from China - in Germ=
any
      up to now without additional tax <img
        src=3D"https://forums.qrz.com/styles/default/xenforo/clear.png"
        class=3D"mceSmilieSprite mceSmilie2" alt=3D";)" title=3D"Wink ;)"=
>;-)
      !<br>
      <br>
      Thanks for all the feedback, 73,<br>
      Tom, DK1IS </p>
  </body>
</html>

--------------D7518291A06D152F8375AFFA--