Message-ID: <4FC53EA6.1060003@iup.uni-heidelberg.de>
Date: Tue, 29 May 2012 23:24:54 +0200
From: =?UTF-8?B?U3RlZmFuIFNjaMOkZmVy?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: 475 kc Exiter
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Sorry Uwe, missed to answer in all the trouble...

I didn't know that a JUMA TX is available for "500".

Well, the version for 137 kHz is fine but i think 60W is not really=20
enough for a ordinary LF amateur antenna. But on MF, 60W may be just=20
right if one want to strictly stay below the limitation of 1W.

Do you know how the PA is designed?

I'm just experimenting with a class D PA for MF but am surprised about=20
the "problems". I.e. i thought it is easier to build. The output C of=20
the FETs cause a heavy oscillation when the FET is OFF. So actually i=20
would prefer a class E which does not have this problem. A class E would=20
be really no problem, regarding the design. But i intend to use it for=20
various experiments, also with /p antennas, just for playing arround.=20
Here, a class E is not recommended at all since it needs a very accurate=20
match to Z=3DR=3D50 Ohm. Otherwise the efficiency is decreasing=20
dramatically, up to blowing up the FET...

73, Stefan/DK7FC

Am 27.05.2012 09:39, schrieb Uwe Wensauer:
> What do You think about the JUMA TX500 TransmitterI
> In my eyes a  small Rig with 60 Watt and built in Converter.
> By the way, have a look at the filters in use =E2=80=93 easy to built a=
n duplicate
> Uwe, dk1kq

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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Sorry Uwe, missed to answer in all the trouble...<br>
<br>
I didn't know that a JUMA TX is available for "500".<br>
<br>
Well, the version for 137 kHz is fine but i think 60W is not really
enough for a ordinary LF amateur antenna. But on MF, 60W may be just
right if one want to strictly stay below the limitation of 1W.<br>
<br>
Do you know how the PA is designed?<br>
<br>
I'm just experimenting with a class D PA for MF but am surprised about
the "problems". I.e. i thought it is easier to build. The output C of
the FETs cause a heavy oscillation when the FET is OFF. So actually i
would prefer a class E which does not have this problem. A class E
would be really no problem, regarding the design. But i intend to use
it for various experiments, also with /p antennas, just for playing
arround. Here, a class E is not recommended at all since it needs a
very accurate match to Z=3DR=3D50 Ohm. Otherwise the efficiency is
decreasing dramatically, up to blowing up the FET...<br>
<br>
73, Stefan/DK7FC<br>
<br>
Am 27.05.2012 09:39, schrieb Uwe Wensauer:
<blockquote cite=3D"mid:8BE4322932454ABBAF36917E7F0B7293@uwePC"
 type=3D"cite">
  <div dir=3D"ltr">
  <div
 style=3D"font-family: 'Calibri'; color: rgb(0, 0, 0); font-size: 12pt;">
  <div>What do You think about the JUMA TX500 TransmitterI</div>
  <div>=C2=A0</div>
  <div>In my eyes a=C2=A0 small Rig with 60 Watt and built in Converter.<=
/div>
  <div>=C2=A0</div>
  <div>By the way, have a look at the filters in use =E2=80=93 easy to bu=
ilt an
duplicate</div>
  <div>=C2=A0</div>
  <div>Uwe, dk1kq</div>
  </div>
  </div>
</blockquote>
</body>
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