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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>HI,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Thanks Phil for clearing/rectification. At the present time the
best approach to better IMD is to use higher supply voltage (48V) and to quit
multi-stage-amp concepts. It’s no problem to produce 300W PEP and more
with a single-stage push-pull configuration driven by Penny/Hermes using modern
LDMOS (gain 28 dB@HF+6m). I measured IMD -33dBc (equal -39 dB PEP, hi).<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>73, Helmut, DC6NY<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>Von:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
hpsdr-bounces@lists.openhpsdr.org [mailto:hpsdr-bounces@lists.openhpsdr.org] <b>Im
Auftrag von </b>FRANCIS CARCIA<br>
<b>Gesendet:</b> Freitag, 18. Januar 2013 02:34<br>
<b>An:</b> hpsdr@lists.openhpsdr.org<br>
<b>Betreff:</b> [hpsdr] HPSDR finals<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='color:black'>Hi All,<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='color:black'>I have
been chasing the IMD monster for a while now. The first thing I needed to do is
adapt the MIL method of measuring IMD because that is what you see in the RX.
The 6dB gift method is a poor interface to the super clean Penny / Hermes
exciter.<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='color:black'>Tiny
transformers do not produce good IMD. Type 61 cores running at less then 150g
and 3 Oe is a good starting point.<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='color:black'>TLT
transformers work much better than the brass tube primary transformers. I'm
very close to -30dB IP3 at 300W PEP.<o:p></o:p></span></p>
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<p class=MsoNormal style='background:white'><span style='color:black'>At 20
Watts I'm around -40dB IP3. I'm running 3 stages of push pull FETS, MRE136,
MRF148, MRF150. The first tuo stages are running class A. There is a good chance I
can eliminate the MRF136 stage because most of the time I have 15dB of
pads between Hermes and the amplifier. I'm also working on a 1200 watt
modified MRI amp with 4 SD2932s. The IMD still needs work but it is on the air.
Predistortion sounds very intereting. Frank WA1GFZ<o:p></o:p></span></p>
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