Message-ID: <571FC141.4030204@posteo.de>
Date: Tue, 26 Apr 2016 21:28:01 +0200
From: DK7FC <selberdenken@posteo.de>
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In-Reply-To: <571F891B.3010109@tele2.se>
Subject: Re: LF: TXing on VLF again, my first homemade linear PA! :-)
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Hi Johan,

Thanks. Fascinating! The modern world, i can just say. I would assume 
such a chip is quite expensive and not easy to get in small amounts(?)
Will you build a PA with that chip for the Dreamers Band (TM) and come 
on air then? It would be fine! Or maybe a RX station? :-)

All the best and nice to read from you again time sometimes.

73, Stefan

Am 26.04.2016 17:28, schrieb Johan Bodin:
> Even more linear QRO for dreamer's band:
>
> http://www.ti.com/lit/ds/symlink/tas5630b.pdf
>
>
> Den 2016-04-26 kl. 17:18, skrev Johan Bodin:
>> Hi Stefan
>>
>> I thought about your 9kHz PA efforts when I found this class D PWM 
>> chip capable of ~300W up to 100kHz with very low distorsion.  Amazing 
>> performance from such a small $6 SMD chip!
>>
>> http://www.ti.com/lit/ds/symlink/tpa3251.pdf
>>
>> 73 de
>> Johan SM6LKM
>>
>> Den 2016-04-23 kl. 18:51, skrev 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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Hi Johan, <br>
<br>
Thanks. Fascinating! The modern world, i can just say. I would assume
such a chip is quite expensive and not easy to get in small amounts(?)<br>
Will you build a PA with that chip for the Dreamers Band (TM) and come
on air then? It would be fine! Or maybe a RX station? :-)<br>
<br>
All the best and nice to read from you again time sometimes.<br>
<br>
73, Stefan<br>
<br>
Am 26.04.2016 17:28, schrieb Johan Bodin:
<blockquote cite="mid:571F891B.3010109@tele2.se" type="cite">
  <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
Even more linear QRO for dreamer's band:<br>
  <br>
  <a moz-do-not-send="true" class="moz-txt-link-freetext"
 href="http://www.ti.com/lit/ds/symlink/tas5630b.pdf">http://www.ti.com/lit/ds/symlink/tas5630b.pdf</a><br>
  <br>
  <br>
  <div class="moz-cite-prefix">Den 2016-04-26 kl. 17:18, skrev Johan
Bodin:<br>
  </div>
  <blockquote cite="mid:571F86BF.5050403@tele2.se" type="cite">
    <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
Hi Stefan<br>
    <br>
I thought about your 9kHz PA efforts when I found this class D PWM chip
capable of ~300W up to 100kHz with very low distorsion.  Amazing
performance from such a small $6 SMD chip!<br>
    <br>
    <a moz-do-not-send="true" class="moz-txt-link-freetext"
 href="http://www.ti.com/lit/ds/symlink/tpa3251.pdf">http://www.ti.com/lit/ds/symlink/tpa3251.pdf</a><br>
    <br>
73 de<br>
Johan SM6LKM<br>
    <br>
    <div class="moz-cite-prefix">Den 2016-04-23 kl. 18:51, skrev DK7FC:<br>
    </div>
    <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>
    <br>
  </blockquote>
  <br>
</blockquote>
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