<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">Good info to know Bill! I run QRO on most bands and I am concerned about getting into the magnetometer, also.<br><br><div dir="ltr"><span style="background-color: rgba(255, 255, 255, 0);"><i><b>73,</b></i><br><i style="font-weight: bold;">Alan Clark, N5PA<br></i>Ellisville, MS<br>Email: <a href="mailto:n5pa@n5pa.com" title="mailto:n5pa@n5pa.com">n5pa@n5pa.com</a><br>URL: <a href="http://www.n5pa.com/" title="http://www.n5pa.com/">http://www.n5pa.com</a></span></div><div dir="ltr"><br><blockquote type="cite">On Jun 30, 2021, at 1:25 PM, Bill Engelke via TangerineSDR <tangerinesdr@lists.tapr.org> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
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<div class="WordSection1">
<p class="MsoNormal">To all:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">You might recall that a few weeks ago I discovered some RF noise appearing on 160 M and 80 M when the magnetometer was hooked up. This was wideband noise on 80M and a birdie on 160M.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Note that I have been using shielded CAT6 cable between the magnetometer base (a Pi-Hat) and the in-ground magnetometer. The noise could be seen clearly in the waterfall on my FlexRadio 6600 connected to my 80M dipole; it was only 1 to
2 s-units, but this might be an issue for DXing.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">It required 2 steps to eliminate this noise:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo1">The ground plane of the R-Pi needs to be connected to an earth ground. This eliminates the birdie on 160M and cuts the 80M noise about in half. Do this by grounding the sleeve of the
R-Pi audio jack.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l1 level1 lfo1">The remaining 80M noise is due to the Canakit switching power supply that comes in a Raspberry Pi kit. To eliminate that, you must replace the switching power supply with a linear
power supply. I found a 4.5 amp linear supply (Pyramid brand, on Amazon $55.79) that has 2 USB jacks (each able to supply 2 amps) plus 13.8 V terminals.*<o:p></o:p></li></ol>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">-73- Bill, AB4EJ<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-left:.25in">* There are cheaper linear power supplies, but R-Pi recommends a supply able to provide 3 amps. Linear power supplies able to provide 3 a are not plentiful or cheap. I measured the actual current pulled by a R-Pi
4 B+, and it is around 1 amp. With the Pyramid supply I am powering two R-Pi 4 B+ computers with power to spare, and the switching noise is gone.<o:p></o:p></p>
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