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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi all,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Also, I mentioned last night the Guide for Magnetic Measurements and Observatory Practice from IAGA (International Association of Geomagnetism and Aeronomy). Here is the link:<o:p></o:p></p><p class=MsoNormal><a href="http://www.iaga-aiga.org/data/uploads/pdf/guides/iaga-guide-observatories.pdf">http://www.iaga-aiga.org/data/uploads/pdf/guides/iaga-guide-observatories.pdf</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>IAGA publishes a number of guides that may be of interest. Here is the complete list:<o:p></o:p></p><p class=MsoNormal><a href="http://www.iaga-aiga.org/publications/guides/">http://www.iaga-aiga.org/publications/guides/</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The IAGA guide is a bit old (1996). So here the current technical reference from intermagnet.org: <a href="https://intermagnet.org/publications/intermag_4-6.pdf">https://intermagnet.org/publications/intermag_4-6.pdf</a><o:p></o:p></p><p class=MsoNormal>I think the IAGA guide is a bit “friendlier” and perhaps more comprehensive, but it is good to have a more current reference as well.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Also, since this is a ham radio group, it is good to remember that ground magnetometer measurements have a strong connection with radio propagation. Most people here are familiar with the Kp index, which is used as a global indicator of geomagnetic storms. One of the largest effects of a geomagnetic storm is an extended depletion of ionospheric densities, which leads to poor propagation on the higher HF bands. The Kp index actually comes from measurements of a network of 13 ground magnetometer stations located around the globe (but not evenly spaced!). See <a href="http://blog.aurorasaurus.org/?p=187">http://blog.aurorasaurus.org/?p=187</a> for a nice description. For a more ham radio perspective, see <a href="https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf">https://www.arrl.org/files/file/Technology/tis/info/pdf/0209038.pdf</a>.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>73 de Nathaniel W2NAF<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b>From:</b> TangerineSDR <tangerinesdr-bounces@lists.tapr.org> <b>On Behalf Of </b>Phil Erickson via TangerineSDR<br><b>Sent:</b> Monday, March 30, 2020 11:41 PM<br><b>To:</b> TAPR TangerineSDR Modular Software Defined Radio <tangerinesdr@lists.tapr.org><br><b>Cc:</b> Phil Erickson <phil.erickson@gmail.com><br><b>Subject:</b> Re: [TangerineSDR] Notes from PSWS / TangerineSDR call of 03-30-2020<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Hi all,<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal> Sorry I missed the call. There is a typo: the field model is IGRF, not IGRFG.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal> IGRF is provided by a series of spherical harmonic coefficients. These are marked for any 5 year interval either as intermediate (IGRF), definitive (DGRF), or predictive (for the current 5 year interval; uses secular change estimates). Usually the coefficients come out every 5 years, but the field was changing so fast that the last update came early in 2019 instead of 2020. A simple code, often in FORTRAN, calculates the field given location and epoch (time).<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>73<o:p></o:p></p></div><div><p class=MsoNormal>Phil W1PJE<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Mon, Mar 30, 2020 at 10:28 PM Tom McDermott via TangerineSDR <<a href="mailto:tangerinesdr@lists.tapr.org">tangerinesdr@lists.tapr.org</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><div><p class=MsoNormal>Notes from PSWS / TangerineSDR call of 03-30-2020<o:p></o:p></p></div><div><p class=MsoNormal>1. Bill has started posting the PSWS / TangerineSDR software to<br><a href="https://github.com/AB4EJ-1/TangerineSDR-notes" target="_blank">https://github.com/AB4EJ-1/TangerineSDR-notes</a><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>2. Kp is determined by a network of magnetometers. This is useful<br>in predicting propagation disturbances. During normal conditions:<o:p></o:p></p></div><div><p class=MsoNormal> At the poles the vertical component should be about 60,000 nT and the<br> horizontal component near zero. At the equator the horizontal component<br> should be about 30,000 nT and the vertical component near zero.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>3. Discussion on magnetometer calibration: how often do they need to be calibrated, and how would this be accomplished?<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>4. International Geomagnetic Reference Field (IGRFG) model profile parameters provides long term estimates of magnetic field by lat/long/height and year:<br><a href="https://ccmc.gsfc.nasa.gov/modelweb/models/igrf_vitmo.php" target="_blank">https://ccmc.gsfc.nasa.gov/modelweb/models/igrf_vitmo.php</a><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>-- Tom, N5EG<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></div><p class=MsoNormal>-- <br>TangerineSDR mailing list<br><a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a><br><a href="http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org" target="_blank">http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org</a><o:p></o:p></p></blockquote></div><p class=MsoNormal><br clear=all><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal>-- <o:p></o:p></p><div><p class=MsoNormal>----<br>Phil Erickson<br><a href="mailto:phil.erickson@gmail.com" target="_blank">phil.erickson@gmail.com</a><o:p></o:p></p></div></div></body></html>