<div dir="ltr"><div><span style="font-family:"arial narrow",sans-serif">Hi HamSCI,</span><br style="font-family:"arial narrow",sans-serif"><br style="font-family:"arial narrow",sans-serif"><span style="font-family:"arial narrow",sans-serif">This week is our bi-weekly HamSCI telecon on Thursday, Feb 04th at 2000z / 3 PM Eastern.</span><br style="font-family:"arial narrow",sans-serif"><br style="font-family:"arial narrow",sans-serif"><span style="font-family:"arial narrow",sans-serif">Here is the link: </span><a href="https://scranton.zoom.us/j/286316405?pwd=QWdwMlFPbDlYeXg5ZDg1dmYzeFdCUT09" target="_blank" style="font-family:"arial narrow",sans-serif">https://scranton.zoom.us/j/286316405?pwd=QWdwMlFPbDlYeXg5ZDg1dmYzeFdCUT09</a></div><div><br style=""><span style="font-family:"arial narrow",sans-serif">If you are asked for a password, it is “hamsci”.</span><br></div><div><span style="font-family:"arial narrow",sans-serif"><br></span></div><div><span style="font-family:"arial narrow",sans-serif">Steve Cerwin WA5FRF,  will give us an update on his recent results from analysing Doppler Frequency and Time of Flight Measurements .</span><br></div><div><br></div><div>Also, we are now accepting abstracts for the 2021 <span class="gmail-il">HamSCI</span> workshop! Please submit at <a href="http://hamsci.org/hamsci2021" target="_blank">http://<span class="gmail-il">hamsci</span>.org/hamsci2021</a><br></div><div><p class="MsoNormal"><u></u></p><br class="gmail-Apple-interchange-newline"></div><div>Best,<br></div><div>Dev</div><div><span style="font-family:"arial narrow",sans-serif"><br></span></div><div><span style="font-family:"arial narrow",sans-serif">-------------------------------------------------------------------------------------------------------------------------</span><br></div><b>Estimation of Ionospheric Layer Height Changes From Doppler Frequency and Time of Flight Measurements on HF Skywave Signals</b><br> -- Steve Cerwin WA5FRF, Kristina Collins KD8OXT, Dev Joshi KC3PVE, Nathaniel Frissell W2NAF<br><br>The HamSCI community has been studying apparent frequency shifts in the reception of HF sky-wave signals from radio station WWV in Ft. Collins, CO. WWV is a standard time and frequency station with atomic clock accuracy. If the receiving station uses a GPS Disciplined Oscillator (GPSDO) for a frequency reference, the atomic clock accuracy on both ends guarantees any observed frequency shifts are attributable only to propagation effects through the ionosphere. Causes for frequency shifts in the received signal are recognized as complex and varied. A leading candidate is Doppler shift resulting from dynamic changes in refraction layer height. These, in turn, are caused by the diurnal transitions between night and day, passage of an eclipse shadow, and ionospheric disturbances originating from solar flares or X-ray events. For the case of changing refraction layer height, an analysis of Doppler frequency and Time of Flight (TOF) data can estimate the changes in skywave path length between the transmitter and receiver. This data can be used in conjunction with an assumed geometric model and propagation mode to infer the corresponding height profile over time. This paper postulates one possible mechanism for observed frequency swings and presents supporting experimental evidence. Comparisons between the calculated height profile and data from ray trace programs and ionosonde measurements are given.<br><div><br></div><div><div style="color:inherit;font-family:inherit;font-style:inherit;font-variant:inherit;font-weight:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;font-size:12pt;line-height:inherit;vertical-align:baseline"><font color="#222222" face="Arial,Helvetica,sans-serif">----------------------------------------------</font></div><div style="color:inherit;font-family:inherit;font-style:inherit;font-variant:inherit;font-weight:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;font-size:12pt;line-height:inherit;vertical-align:baseline"><b style="color:black;font-size:12pt;font-family:Calibri,Arial,Helvetica,sans-serif;font-variant-caps:inherit;font-variant-ligatures:inherit"><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:12pt;line-height:inherit;font-family:Arial,Helvetica,sans-serif;vertical-align:baseline;color:rgb(34,34,34)">Dev Joshi, Ph.D., </span></b><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:large;line-height:inherit;vertical-align:baseline"><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:12pt;line-height:inherit;vertical-align:baseline;color:inherit">KC3PVE</span></span><br></div><span style="color:inherit;font-family:inherit;font-style:inherit;font-variant:inherit;font-weight:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;font-size:12pt;line-height:inherit;vertical-align:baseline"></span><div style="font-style:inherit;font-variant:inherit;font-weight:inherit;margin:0px;padding:0px;border:0px;font-stretch:inherit;font-size:12pt;line-height:inherit;font-family:Calibri,Arial,Helvetica,sans-serif;vertical-align:baseline;color:black"><div style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:inherit"><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:rgb(102,102,102)">Postdoctoral Research Associate</span></div><div style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:inherit"><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:rgb(102,102,102)">Department of Physics and Engineering</span></div><div style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:inherit"><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:rgb(102,102,102)">The University of Scranto</span><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:rgb(102,102,102)">n</span></div><div style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:inherit"><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:rgb(102,102,102)">C:</span><span style="margin:0px;padding:0px;border:0px;font:inherit;vertical-align:baseline;color:inherit"> 617 775 9712</span></div></div></div></div>