Message-ID: <4FC7596E.4070806@iup.uni-heidelberg.de>
Date: Thu, 31 May 2012 13:43:42 +0200
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 <Stefan.Schaefer@iup.uni-heidelberg.de>
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References: <8BE4322932454ABBAF36917E7F0B7293@uwePC> <CAMFjj70+gM-ukas=NGMLyYwpL_wKnr-Mx3B6JH23XTr7yk_k9A@mail.gmail.com> <4FC74C16.1050905@iup.uni-heidelberg.de> <034701cd3f1d$b69fa650$1502a8c0@Clemens04>
In-Reply-To: <034701cd3f1d$b69fa650$1502a8c0@Clemens04>
Subject: Re: LF: 475 kc Exiter /JUMA
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Hi Clemens,

Oh, OK. But anyway it was a very good hint to mention the JUMA 500 TX 
since it leads me to the CMCD design and this paper which nicely 
describes the problem of the VMCD desgin which i am trying in my first 
tests.
The output C of the FETs is the problem. Since i want to have a 
relatively high power (100W) at 12V DC, the primary impedance is very 
low. So i have to use FETs with a very low on-resistance, ideally as low 
as possible of course. To find them is no problem (e.g. IRFP4368 
<http://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/IRFP4368PbF.pdf>), 
but the output C is much to high then. I tried a IRZF48N (2 of them of 
course) as a compromise between RDSon and Cout but am just getting 60% 
efficiency at 70W in the first attempt. That's not acceptable for a /p 
PA that has to stay compact, i.e. without a big heat sink and/or a fan...

The basics are well explained in this paper, makes fun to read :-)

73, Stefan/DK7FC

Am 31.05.2012 13:08, schrieb Clemens Paul:
>> It costs 300 Euro which is not to much.
>
> Unfortunately you have to add 23%VAT tax within EU and shipping costs
> which I estimate to 30-40 Euro.
> So we end up somewhere around 400 Euro.
> Interesting kit,though.
>
> 73
> Clemens
> DL4RAJ
>
>

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Hi Clemens, <br>
<br>
Oh, OK. But anyway it was a very good hint to mention the JUMA 500 TX
since it leads me to the CMCD design and this paper which nicely
describes the problem of the VMCD desgin which i am trying in my first
tests.<br>
The output C of the FETs is the problem. Since i want to have a
relatively high power (100W) at 12V DC, the primary impedance is very
low. So i have to use FETs with a very low on-resistance, ideally as
low as possible of course. To find them is no problem (e.g. <a
 href="http://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/IRFP4368PbF.pdf">IRFP4368</a>),
but the output C is much to high then. I tried a IRZF48N (2 of them of
course) as a compromise between RDSon and Cout but am just getting 60%
efficiency at 70W in the first attempt. That's not acceptable for a /p
PA that has to stay compact, i.e. without a big heat sink and/or a
fan...<br>
<br>
The basics are well explained in this paper, makes fun to read :-)<br>
<br>
73, Stefan/DK7FC<br>
<br>
Am 31.05.2012 13:08, schrieb Clemens Paul:
<blockquote cite="mid:034701cd3f1d$b69fa650$1502a8c0@Clemens04"
 type="cite">
  <blockquote type="cite">It costs 300 Euro which is not to much.
    <br>
  </blockquote>
  <br>
Unfortunately you have to add 23%VAT tax within EU and shipping costs
  <br>
which I estimate to 30-40 Euro.
  <br>
So we end up somewhere around 400 Euro.
  <br>
Interesting kit,though.
  <br>
  <br>
73
  <br>
Clemens
  <br>
DL4RAJ
  <br>
  <br>
  <br>
</blockquote>
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