<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Hi Phil -- can you clarify whether the TAPR-built units have that change?</div><div><br></div><div>Thanks!</div><div><br></div><div>John</div><div><br>On Feb 24, 2013, at 3:59 AM, "Phil Harman" <<a href="mailto:phil@pharman.org">phil@pharman.org</a>> wrote:<br><br></div><blockquote type="cite"><div><span>***** High Performance Software Defined Radio Discussion List *****</span><br><span></span><br></div></blockquote><blockquote type="cite"><div>
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<div>Hi Tokio,</div>
<div> </div>
<div>Thanks for your comments. Later versions of the Hermes board did
change R141 from 100 ohms to 51 ohms in order to operate more reliably using an
external 10 MHz reference. </div>
<div> </div>
<div>73 Phil....VK6APH </div>
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<div style="font-color: black"><b>From:</b> <a title="rfcgf600@ybb.ne.jp" href="mailto:rfcgf600@ybb.ne.jp">Tokio Endo</a> </div>
<div><b>Sent:</b> Sunday, February 24, 2013 4:54 PM</div>
<div><b>To:</b> <a title="hpsdr@openhpsdr.org" href="mailto:hpsdr@openhpsdr.org">hpsdr@openhpsdr.org</a> </div>
<div><b>Subject:</b> [hpsdr] Resistor value to be changed: R141 of
Hermes</div></div></div>
<div> </div></div>
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<div><font size="2" face="Arial"><span class="078073308-24022013">Hi
All,</span></font></div>
<div><span class="078073308-24022013"><font face="Arial"><span class="468582402-23022013"></span></font> </span></div>
<div>
<div><font size="2" face="Arial"><span class="468582402-23022013">I use Hermes by
using External 10MHz clock.</span></font></div>
<div><span class="468582402-23022013"></span><span class="468582402-23022013"><span class="468582402-23022013"><font face="Arial"><font size="2">Recently I noticed
receiving CW tonality abruptly changed in a very very short period.<span class="078073308-24022013"> It's very
subtle.</span></font></font></span></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">Then I hooked a probe of
an oscilloscoe on JP20 to see the shapes of the clock, when External or
Internal.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">The differecne between
the both is quite apparent, the output level of two transistor's wave shapping
circuit for External clock is low.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013"></span></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">By sharing this
phenomenon with Phil, VK6APH, I changed the value of R141 from original 100 ohms
to 51 ohms.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">The result is OK, the
level is almost same as External clock's one.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013"></span></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">According to the
schematics of Hermes as well as BOM, R141 is 100 ohms, but in my case it doesn't
work properly.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013"></span></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">If you use External
clock, check the value of R141 and see the clock shape of JP20 at JP20 if an
oscilloscope is available.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013"></span></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">If there is a difference
compared with Internal clock shape, I recommend you to change the value of R141
to 51 ohms.</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013"></span></span></font></span> </div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">73,</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">Tokio
Endo</span></span></font></span></div>
<div><span class="468582402-23022013"><font size="2" face="Arial"><span class="468582402-23022013"><span class="078073308-24022013">JA1CCA</span></span></font></span></div>
<div>
<div><font size="2" face="Arial"><span class="468582402-23022013"></span></font> </div>
<div><font size="2" face="ＭＳ Ｐゴシック"></font> </div></div></div>
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