Message-ID: <571CD297.4070107@posteo.de>
Date: Sun, 24 Apr 2016 16:05:11 +0200
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: LF: TXing on VLF again, my first homemade linear PA! :-)
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VLF,

The carrier has been on the air from 23:30 to 14:00 UTC, hopefully with 
a stable phase (no glitches).
I can see weak traces on the DF6NM grabber but all in all it looks quite 
poor :-(
I'm now trying to prepare for a first EbNaut transmission...

73, Stefan

Am 23.04.2016 18:51, schrieb DK7FC:
> Hi all,
>
> Since about 16 UTC i'm transmitting on 8270.00500 Hz again. The 
> antenna current is about 200 mA. It is a first test over a longer time 
> with my new PA.
>
> I have been off the air for a few days now becuase i destroyed my 
> audio amp that i used as a VLF PA. Somehow i started to like the idea 
> of a clean sine wave coming from the PA. Low pass filters are hard to 
> design for VLF, you know. Since i don't like buying and since i didn't 
> find another one in the trash, i 'had to' (actually /wanted/) to build 
> my own. It is a class-AB PA now running at 20V DC using 2x IRFP064N 
> against ground. Opposite phase drive signals are generated by a small 
> blue ferrite core with 20 quadfilar turns. On the primary side, 2 of 
> these 4 windings are in series. On the scope, the signal looks quite 
> good. The 3rd harmonic is at about -20 dBc, certainly improvable. But 
> it's just version 0.2 now ;-)
> A large ferrite core is used to up-transform the voltage to about 220V 
> rms for this power level (i'm not spot on the resonance), also 
> providing galvanic decoupling.
>
> A photo can be found at
> https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg
> https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg
>
> The PA consumes 3.6A at 20V DC now. Improvements will follow...
>
> The signal will stay on air for a few hours now.
>
> 73, Stefan

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VLF, <br>
<br>
The carrier has been on the air from 23:30 to 14:00 UTC, hopefully with
a stable phase (no glitches). <br>
I can see weak traces on the DF6NM grabber but all in all it looks
quite poor :-(<br>
I'm now trying to prepare for a first EbNaut transmission...<br>
<br>
73, Stefan<br>
<br>
Am 23.04.2016 18:51, schrieb DK7FC:
<blockquote cite="mid:571BA7FE.6080601@posteo.de" type="cite">
  <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
Hi all, <br>
  <br>
Since about 16 UTC i'm transmitting on 8270.00500 Hz again. The antenna
current is about 200 mA. It is a first test over a longer time with my
new PA.<br>
  <br>
I have been off the air for a few days now becuase i destroyed my audio
amp that i used as a VLF PA. Somehow i started to like the idea of a
clean sine wave coming from the PA. Low pass filters are hard to design
for VLF, you know. Since i don't like buying and since i didn't find
another one in the trash, i 'had to' (actually <i>wanted</i>) to build
my own. It is a class-AB PA now running at 20V DC using 2x IRFP064N
against ground. Opposite phase drive signals are generated by a small
blue ferrite core with 20 quadfilar turns. On the primary side, 2 of
these 4 windings are in series. On the scope, the signal looks quite
good. The 3rd harmonic is at about -20 dBc, certainly improvable. But
it's just version 0.2 now ;-) <br>
A large ferrite core is used to up-transform the voltage to about 220V
rms for this power level (i'm not spot on the resonance), also
providing galvanic decoupling.<br>
  <br>
A photo can be found at <br>
  <a moz-do-not-send="true" class="moz-txt-link-freetext"
 href="https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg">https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184046.jpg</a><br>
  <a moz-do-not-send="true" class="moz-txt-link-freetext"
 href="https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg">https://dl.dropboxusercontent.com/u/19882028/VLF/20160423_184059.jpg</a><br>
  <br>
The PA consumes 3.6A at 20V DC now. Improvements will follow...<br>
  <br>
The signal will stay on air for a few hours now.<br>
  <br>
73, Stefan<br>
</blockquote>
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