<div dir="ltr">Was the test unit powered by a switching power supply module? If so, replacing it with a linear supply might help.<div><br></div><div>In a "production configuration" we should recommend shielded CAT5 or CAT6 cable with type 31 ferrite beads or cores on each end of the Ethernet cable. If practical, a linear power supply should be used for both the magnetometer module and the host SDR. There are clean switchmode supplies, as well, but they would have to be tested.</div><div><br></div><div>If the noise is being radiated directly from the electronics, we'll have to tackle that separately.</div><div><br></div><div>73, Ward N0AX</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jun 2, 2021 at 8:39 AM Dr. Nathaniel A. Frissell Ph.D. <<a href="mailto:nathaniel.frissell@scranton.edu">nathaniel.frissell@scranton.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div style="overflow-wrap: break-word;">
Hi Bill,
<div><br>
</div>
<div>Thank you for that evaluation, and like Ward, I am glad to hear the magnetometer does not appear to be sensitive to RF. I’m sorry to hear about its effects on 80 and 160 m, and I guess that will need to be discussed some more.</div>
<div><br>
</div>
<div>73 Nathaniel W2NAF</div>
<div><br>
<div>
<div>— <br>
Dr. Nathaniel A. Frissell, Ph.D., W2NAF</div>
<div>HamSCI Lead<br>
Assistant Professor<br>
Department of Physics and Electrical Engineering<br>
University of Scranton<br>
(973) 787-4506</div>
</div>
<div><br>
<blockquote type="cite">
<div>On Jun 1, 2021, at 10:09 PM, Ward Silver via TangerineSDR <<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>> wrote:</div>
<br>
<div>
<div dir="ltr">Glad to hear of the insensitivity to ambient RF at a variety of frequencies, Bill!
<div><br>
</div>
<div>This brings up the system-level issue of RFI created by the PSWS as conducted emissions, most likely. It would be a problem if the PSWS interferes with its own local receiver! So we (meaning the design team) will need to carefully evaluate the
I/O and power lines to be sure they are RF-quiet. I can probably help with that as I am winding down a series of back-to-back-to-back book projects and have some time coming up.</div>
<div><br>
</div>
<div>73, Ward N0AX</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Jun 1, 2021 at 9:00 PM <<a href="mailto:tangerinesdr-request@lists.tapr.org" target="_blank">tangerinesdr-request@lists.tapr.org</a>> wrote:<br>
</div>
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Today's Topics:<br>
<br>
1. Magnetometer RF testing, additional results (Bill Engelke)<br>
<br>
<br>
----------------------------------------------------------------------<br>
<br>
Message: 1<br>
Date: Tue, 1 Jun 2021 16:15:00 +0000<br>
From: Bill Engelke <<a href="mailto:bill.engelke@ua.edu" target="_blank">bill.engelke@ua.edu</a>><br>
To: TAPR TangerineSDR Modular Software Defined Radio<br>
<<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>><br>
Subject: [TangerineSDR] Magnetometer RF testing, additional results<br>
Message-ID:<br>
<<a href="mailto:BN8PR15MB31855B741907BD4C37902902FA3E9@BN8PR15MB3185.namprd15.prod.outlook.com" target="_blank">BN8PR15MB31855B741907BD4C37902902FA3E9@BN8PR15MB3185.namprd15.prod.outlook.com</a>><br>
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Content-Type: text/plain; charset="us-ascii"<br>
<br>
Here is a follow-up to my last email regarding possible RF interactions with the magnetometer. A couple of suggestions came in from the community:<br>
<br>
<br>
1. Ward Silver, N0AX, recommended to test by transmitting with a dipole near the magnetometer in several configurations, on 2 meters with 50 w.<br>
2. Tom McDermott, N5EG, recommended to look for RF noise being generated by the magnetometer that might get into your station receiver.<br>
<br>
Here are results of doing such tests:<br>
<br>
<br>
1. I built a 2-m dipole specifically for this so that I could test with the antenna (a)broadside to the magnetometer, (b)vertical to it, and (c) pointed towards it. (photos) The antenna was located about 10 feet from the magnetometer, which is buried at
2 feet in the soil (its standard installation as tested by Jules and others), and connected to the station with shielded CAT-6.<br>
<br>
Broadside configuration<br>
<br>
[<a>cid:image004.png@01D756D6.2EB4CD30</a>]<br>
<br>
Vertical configuration:<br>
<br>
[<a>cid:image005.png@01D756D7.049AA500</a>]<br>
<br>
Straight-on configuration<br>
<br>
[<a>cid:image006.png@01D756D7.049AA500</a>]<br>
<br>
The antenna was connected via a new 50 foot RG-8 cable to an Icom IC-706MKIIG, set to high output (50 watts), 145 MHz. I did my best to do what Ward suggested.<br>
<br>
Results: I never saw the magnetometer readings change when I keyed the rig; this was the same for the 3 different antenna angles. I have to conclude that the magnetometer is not sensitive to 2 meters.<br>
<br>
<br>
1. Using the FlexRadio 6600, I looked for noise being generated by the magnetometer on all ham bands from 160 m to 10 meters. I looked for wide band noise by watching the waterfall and turning the magnetometer on and off. If I saw noise appear, I tried turning
the magnetometer off and on to see if the noise would come and go with being connected to the magnetometer base card on the Raspberry Pi. I used the appropriate antenna for each band (i.e., the one I use for my station), as follows: (160 M) - multiband vertical,
(80M) halfwave dipole at 15 ' (20 feet away) and also multiband vertical about 50' away, (60M) multiband vertical, (40 M) double bazooka inverted vee, (20M through 10 M) DX Engineering Hexbeam on 50' tower.<br>
<br>
Results: First the good news: I never saw wideband noise attributable to the magnetometer on the bands 60 meters and higher in frequency. I did see noise on 80M and on 160M. The magnetometer does generate noise of about 0.4 db as shown on the FlexRadio s-meter
on 80M. (Note that this is a severe case, as the 80 M dipole is only up 15' and about 20' away from the magnetometer - but this is probably a typical situation). On 160 M, the magnetometer generated 1 db of noise.<br>
<br>
Screenshot of 80 M result using dipole<br>
<br>
[<a>cid:image001.png@01D756D4.9FD34E80</a>]<br>
<br>
Screenshot of 80 M on multiband vertical<br>
<br>
[<a>cid:image002.png@01D756D5.12202BC0</a>]<br>
<br>
Screenshot of 160 M, multiband vertical<br>
<br>
[<a>cid:image003.png@01D756D5.6F866360</a>]<br>
<br>
I suppose that we would recommend turning off the magnetometer if you are working DX on 80 Meters; possibly separating the magnetometer from the antenna might also help, but I was not able to test that.<br>
<br>
-73- Bill, AB4EJ<br>
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