Message-ID: <50784744.5020705@psk31.plus.com>
Date: Fri, 12 Oct 2012 17:37:24 +0100
From: g3zjo <g3zjo@psk31.plus.com>
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To: rsgb_lf_group@blacksheep.org
References: <50783F5D.60809@iup.uni-heidelberg.de>
In-Reply-To: <50783F5D.60809@iup.uni-heidelberg.de>
Subject: Re: LF: WSPR on the 630m band
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Hi Stefan

I see what you mean, so we have both been at it, (upsetting Mal some 
more).:-)

What a beautiful clear clean bench surface you have, I had to carefully 
frame my pictures after pushing aside the clutter.

http://photobucket.com/albums/dd243/radiotalk/xbmxvtr500ksml.jpg

73

Eddie G3ZJO



On 12/10/2012 17:03, Stefan Schäfer wrote:
> MF!
>
> Last night i built a transmit converter which allows me to transmit 
> *WSPR on 630m* now.
>
> Yes yes yes yes yes Mal, CW is preferred! But many OMs go to bed quite 
> early i find. Not so their PCs, they run over night, and so my 
> transmitter will do this weekend if all goes right. :-) I'm not 
> present in the shack anyway, so no chance for CW...
>
> I'm using _*normal WSPR*_, not the slow versions.
>
> Right now the first tests are running and i check if the system 
> becomes to warm.
>
> The design of this mixer is quite chaotic but i like it :-) It is a 
> modular system...: First, a tone of 14700 Hz is generated by the WSPR 
> program. Is is decoupled from anything by an audio isolating 
> transformer. This signal is applied to a SA612 mixer. The LO (461 kHz) 
> in this test setup comes fom my DDS VFO which is used in the first VLF 
> experiments. The output looks very well as expected on the scope. 
> Filtering of mixing products is done in my MF meachanical filter which 
> is use in front of the receiver normally! I've published the nearly 
> perfect filter curve some weeks ago. Of course the sine wave coming 
> out from the filter looks very well! This sine wave is applied to an 
> OP AMP which is switched as a comparator. I've added a small 
> hysteresis (10 MOhm / 47k) to prevent an oscillating output when there 
> is no input signal. Works well! The output of the OP AMP is fed to a 
> ICL7667 (FET driver) which makes a low impedant output. In series with 
> 1 Ohm and 1 uF this rectanfgular waveform is applied to a small 
> ferrite toroid with a trifilar winding. So this output is again 
> galvanically decoupled from the circuit and provides an opposite phase 
> rectangular signal at 475.7 kHz.
> Since my PA was/is designed to have a 4f input (1900 kHz -> 475 kHz 
> out) i had to make a tap behind the divider, so i have to take care to 
> maintain the 50 % duty cycle in the new circuit. The new external 
> drive signal from the converter is applied by a simple headphone 
> jack/plug! I actually found a 3.5mm stereo-jack with dimensions 10mm x 
> 5mm and also found a few holes to add this on the board. So the PA is 
> now able to run as before and additionally with this new converter......
>
> The AF signal levels and the LO signal level is critical. Choosing 
> wrong values will change the 50% duty cycle which will quickly kill 
> the FETs in this PA design. So i'm using an old modified PC power 
> supply that will shut down quickly if the current exceeds a certain 
> limit...
>
> After writing this email the PA became hand warm so it looks all fine. 
> I will go down to 50% TX duty cycle now and even receive during the 
> breaks in WSPR. However the MF filter is now used for the TX so the RX 
> performance may be slightly lowered...
>
> *Reports about my transmissions on 475.700 kHz are very welcomed. I'm 
> also receiving and uploading to the WSPR database...
> Maybe i will run the test until monday :-)*
>
> Best 73, Stefan/DK7FC
>
> PS: https://dl.dropbox.com/u/19882028/MF/stuff.JPG
>
> No virus found in this message.
> Checked by AVG - www.avg.com <http://www.avg.com>
> Version: 2012.0.2221 / Virus Database: 2441/5327 - Release Date: 10/12/12
>


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    Hi Stefan<br>
    <br>
    I see what you mean, so we have both been at it, (upsetting Mal some
    more).<span class="moz-smiley-s1"><span> :-) </span></span><br>
    <br>
    What a beautiful clear clean bench surface you have, I had to
    carefully frame my pictures after pushing aside the clutter.<br>
    <br>
    <a class="moz-txt-link-freetext" href="http://photobucket.com/albums/dd243/radiotalk/xbmxvtr500ksml.jpg">http://photobucket.com/albums/dd243/radiotalk/xbmxvtr500ksml.jpg</a><br>
    <br>
    73<br>
    <br>
    Eddie G3ZJO<br>
    <br>
    <br>
    <br>
    On 12/10/2012 17:03, Stefan Schäfer wrote:
    <blockquote cite="mid:50783F5D.60809@iup.uni-heidelberg.de"
      type="cite">
      <meta http-equiv="content-type" content="text/html;
        charset=ISO-8859-15">
      MF!<br>
      <br>
      Last night i built a transmit converter which allows me to
      transmit <b>WSPR
        on 630m</b> now.<br>
      <br>
      Yes yes yes yes yes Mal, CW is preferred! But many OMs go to bed
      quite
      early i find. Not so their PCs, they run over night, and so my
      transmitter will do this weekend if all goes right. :-) I'm not
      present
      in the shack anyway, so no chance for CW...<br>
      <br>
      I'm using <u><b>normal WSPR</b></u>, not the slow versions.<br>
      <br>
      Right now the first tests are running and i check if the system
      becomes
      to warm.<br>
      <br>
      The design of this mixer is quite chaotic but i like it :-) It is
      a
      modular system...: First, a tone of 14700 Hz is generated by the
      WSPR
      program. Is is decoupled from anything by an audio isolating
      transformer. This signal is applied to a SA612 mixer. The LO (461
      kHz)
      in this test setup comes fom my DDS VFO which is used in the first
      VLF
      experiments. The output looks very well as expected on the scope.
      Filtering of mixing products is done in my MF meachanical filter
      which
      is use in front of the receiver normally! I've published the
      nearly
      perfect filter curve some weeks ago. Of course the sine wave
      coming out
      from the filter looks very well! This sine wave is applied to an
      OP AMP
      which is switched as a comparator. I've added a small hysteresis
      (10
      MOhm / 47k) to prevent an oscillating output when there is no
      input
      signal. Works well! The output of the OP AMP is fed to a ICL7667
      (FET
      driver) which makes a low impedant output. In series with 1 Ohm
      and 1
      uF this rectanfgular waveform is applied to a small ferrite toroid
      with
      a trifilar winding. So this output is again galvanically decoupled
      from
      the circuit and provides an opposite phase rectangular signal at
      475.7
      kHz. <br>
      Since my PA was/is designed to have a 4f input (1900 kHz -&gt; 475
      kHz
      out) i had to make a tap behind the divider, so i have to take
      care to
      maintain the 50 % duty cycle in the new circuit. The new external
      drive
      signal from the converter is applied by a simple headphone
      jack/plug! I
      actually found a 3.5mm stereo-jack with dimensions 10mm x 5mm and
      also
      found a few holes to add this on the board. So the PA is now able
      to
      run as before and additionally with this new converter......<br>
      <br>
      The AF signal levels and the LO signal level is critical. Choosing
      wrong values will change the 50% duty cycle which will quickly
      kill the
      FETs in this PA design. So i'm using an old modified PC power
      supply
      that will shut down quickly if the current exceeds a certain
      limit...<br>
      <br>
      After writing this email the PA became hand warm so it looks all
      fine.
      I will go down to 50% TX duty cycle now and even receive during
      the
      breaks in WSPR. However the MF filter is now used for the TX so
      the RX
      performance may be slightly lowered...<br>
      <br>
      <b>Reports about my transmissions on 475.700 kHz are very
        welcomed. I'm
        also receiving and uploading to the WSPR database...<br>
        Maybe i will run the test until monday :-)</b><br>
      <br>
      Best 73, Stefan/DK7FC<br>
      <br>
      PS: <a moz-do-not-send="true" class="moz-txt-link-freetext"
        href="https://dl.dropbox.com/u/19882028/MF/stuff.JPG">https://dl.dropbox.com/u/19882028/MF/stuff.JPG</a><br>
      <p class="" avgcert""="" color="#000000" align="left">No virus
        found in this message.<br>
        Checked by AVG - <a moz-do-not-send="true"
          href="http://www.avg.com">www.avg.com</a><br>
        Version: 2012.0.2221 / Virus Database: 2441/5327 - Release Date:
        10/12/12</p>
    </blockquote>
    <br>
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