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Date: Sun, 29 Dec 2013 17:12:58 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: VLF exciter
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Hi Wolf,

Am 29.12.2013 12:18, schrieb wolf_dl4yhf:
> Hello Markus,
>
> Ok .. i had assumed the problem was the flipflop (or binary frequency 
> divider) which would be in an unpredictable state when not fed with a 
> phase-coherent signal "in the gaps" (zeroes in the Opera- or whatever 
> amplitude keyed signal).
> This could be solved by providing the auxiliary output from the 
> soundcard (at 2 * f_tx), to keep the divider chain running.

You are right, this is the "problem". Actually there are no problems, 
just interesting jobs :-)

> Depending on the MOSFET gate drivers, it may also be possible to feed 
> the 'keying signal' to an output-enable-signal, but I'm not sure if 
> that would put the driver output in high-impedance state (which would 
> result in a catastrophic 'bang' if both FET gates were left floating).
The MOSFET driver is an IR2113 which has of course an enable pin. 
However i need the PTT signal anyway and if just tones are coming from 
the soundcard then this is no solution and i will need a constant, 
uninterrupted tone and another tone for the VOX, as you say.


> (p.s. just managed to build a transformer for a low-voltage MF PA, 
> which transforms 0.6 Ohms drain load impedance to 12.5 Ohm with very 
> low stray inductance.. using copper foil instead of wire, and thin 
> adhesive tape ("Tesafilm") as insulator. But that's another story..)
Hmm, P ~ 300W? :-)
An alternative to the foil could be: 4x 
http://www.reichelt.de/index.html?ACTION=3;ARTICLE=57209;SEARCH=CLI 200/120

73, Stefan

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Hi Wolf, <br>
<br>
Am 29.12.2013 12:18, schrieb wolf_dl4yhf:
<blockquote cite="mid:52C00514.4030805@freenet.de" type="cite">
  <meta content="text/html; charset=ISO-8859-1"
 http-equiv="Content-Type">
  <div class="moz-cite-prefix">Hello Markus,<br>
  <br>
Ok .. i had assumed the problem was the flipflop (or binary frequency
divider) which would be in an unpredictable state when not fed with a
phase-coherent signal "in the gaps" (zeroes in the Opera- or whatever
amplitude keyed signal).<br>
This could be solved by providing the auxiliary output from the
soundcard (at 2 * f_tx), to keep the divider chain running.<br>
  </div>
</blockquote>
<br>
You are right, this is the "problem". Actually there are no problems,
just interesting jobs :-)<br>
<br>
<blockquote cite="mid:52C00514.4030805@freenet.de" type="cite">
  <div class="moz-cite-prefix"> Depending on the MOSFET gate drivers,
it may also be possible to feed the 'keying signal' to an
output-enable-signal, but I'm not sure if that would put the driver
output in high-impedance state (which would result in a catastrophic
'bang' if both FET gates were left floating). <br>
  </div>
</blockquote>
The MOSFET driver is an IR2113 which has of course an enable pin.
However i need the PTT signal anyway and if just tones are coming from
the soundcard then this is no solution and i will need a constant,
uninterrupted tone and another tone for the VOX, as you say.<br>
<br>
<br>
<blockquote cite="mid:52C00514.4030805@freenet.de" type="cite">
  <div class="moz-cite-prefix"> (p.s. just managed to build a
transformer for a low-voltage MF PA, which transforms 0.6 Ohms drain
load impedance to 12.5 Ohm with very low stray inductance.. using
copper foil instead of wire, and thin adhesive tape ("Tesafilm") as
insulator. But that's another story..)<br>
  </div>
</blockquote>
Hmm, P ~ 300W? :-)<br>
An alternative to the foil could be: 4x
<a class="moz-txt-link-freetext" href="http://www.reichelt.de/index.html?ACTION=3;ARTICLE=57209;SEARCH=CLI">http://www.reichelt.de/index.html?ACTION=3;ARTICLE=57209;SEARCH=CLI</a>
200/120<br>
<br>
73, Stefan<br>
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