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<div><b>From:</b> Andy Wallace <soldersmoke01@gmail.com></div><div><b>To:</b> Paul Pellegrini <k1vk@yahoo.com></div><div><b>Sent:</b> Friday, December 4, 2020, 09:16:55 AM EST</div><div><b>Subject:</b> Re: [bars] Fwd: Monitor RFI</div><div><br></div>
<div><div id="ydp23cd0744yiv6288223531"><div><div dir="ltr">Thanks! You did not cc the List by the way. I hope Gary can solve it...Per Amndy's suggestoin</div><div dir="ltr">Andy</div><div dir="ltr"><br clear="none"></div><div dir="ltr"><div class="ydp23cd0744yiv6288223531yqt7348740863" id="ydp23cd0744yiv6288223531yqtfd67979"><br clear="none">On Dec 4, 2020, at 8:53 AM, Paul Pellegrini <k1vk@yahoo.com> wrote:<br clear="none"><br clear="none"></div></div><div class="ydp23cd0744yiv6288223531yqt7348740863" id="ydp23cd0744yiv6288223531yqtfd83673"><div dir="ltr"><div class="ydp23cd0744yiv6288223531ydp8b45b038yahoo-style-wrap" style="font-family:times new roman, new york, times, serif;font-size:16px;"><div></div>
<div dir="ltr">Andy -</div><div dir="ltr"><br clear="none"></div><div dir="ltr">This is great information. RFI suppression is important even for low power levels. I've had problems with LCD computer screens at the 100 watt RF power level. The problem I had was caused by RF signal pickup by the wall power cord. Two clamp on filters on the AC cord solved the problem.</div><div dir="ltr"><br clear="none"></div><div dir="ltr"><span><span style="color:rgb(0, 0, 0);font-family:times new roman, new york, times, serif;font-size:16px;">Another source of different types of ferrite materials is Palomar Engineers.</span></span><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr"><a shape="rect" href="https://palomar-engineers.com/" rel="nofollow" target="_blank">https://palomar-engineers.com/</a><br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">They sell both toroid material and completed filters.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">73 de K1VK</div><div dir="ltr">Paul</div><div><br clear="none"></div>
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On Thursday, December 3, 2020, 09:03:42 AM EST, Andy Wallace <soldersmoke01@gmail.com> wrote:
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">Gary W1GFF’s issue with RFI into his computer monitor sent me surfing. This site has some interesting tips about suspecting that it could be common mode current from the transmitter. Here is info on making a detector for that.</p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal"><a shape="rect" href="https://ham.stackexchange.com/questions/1271/how-to-detect-common-mode-currents-or-rf-in-the-shack" rel="nofollow" target="_blank">rfi - How to detect common-mode currents or “RF in the shack”? - Amateur Radio Stack Exchange</a></p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">A comment here said that connecting an SWR analyzer and running your hand along the feedline could be a good test for this (without needing a transmitter). Gary, the fact it happens on 20 is the biggest clue. How is the native SWR there?
A field strength meter might help, too. Good luck – sometimes these things are hard to troubleshoot but at least these devices are in your house, not a neighbor’s!</p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal"><span style="font-size:10.0pt;font-family:sans-serif;">Here is K9YC’s excellent presentation on making your own coax chokes.
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal"><a shape="rect" href="https://www.qsl.net/w/wa3mej/Articles/K9YC/CoaxChokesPPT.pdf" rel="nofollow" target="_blank">Microsoft PowerPoint - CoaxChokes-SCRZ.ppt (qsl.net)</a></p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">W1HIS’s presentation on common mode chokes is here:</p>
<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal"><a shape="rect" href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiftbfh-rHtAhXNo54KHTw0BXcQFjAAegQIBBAC&url=http%3A%2F%2Fwww.yccc.org%2FArticles%2FW1HIS%2FCommonModeChokesW1HIS2006Apr06.pdf&usg=AOvVaw01V9lcrYhYR0cAa59vCB3b" rel="nofollow" target="_blank">Common-Mode
Chokes - Yankee Clipper Contest Club www.yccc.org › Articles › W1HIS › CommonModeCh... (google.com)</a></p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">And as people have mentioned, the #43 cores are not as good as the #31 for the lower HF bands. I have ordered 31s direct from Mouser and Digikey by putting in the Fair-Rite part numbers in the search. Do NOT be ripped off by ebay and other
sellers who call these things “FT240-31” and whack you $20 for a single donut. They are about $5 at the previous sites.
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">Hope these help. </p>
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<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">Andy</p>
<p class="ydp23cd0744yiv6288223531ydp4db19508yiv7160076960MsoNormal">KA1GTT<span style="font-size:10.0pt;font-family:sans-serif;"></span></p>
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