WWV Time Tick Arrival Time Study to Investigate Multiple Modes During Daily Dawn and Dusk Transitions

High resolution spectral waterfall measurements of the 5 MHz WWV carrier frequency from Ft. Collins, CO to San Antonio, TX have shown the carrier to divide into the primary and additional frequency shifted copies during the night to day sunrise transition. In many cases the morning positive Doppler shifts associated with these frequencies appeared to follow a geometric progression. This timing study was conducted in an effort to learn more about multipath propagation during the dawn and dusk transitions. Timing measurements were made to arrival times of the first and delayed copies WWV 1‐second timing ticks referenced to the 1 pps timing pulse available from a GPS Disciplined Oscillator. The primary and delayed arrival times were observed to cluster in a geometric progression that were consistent with ray trace programs predicting Time‐Of‐Flight for 1, 2, and 3 hop propagation modes. This talk presents the measurement techniques used, measured data for January 29, 2020, and correlations with a simplified geometric analysis, PHaRLAP, and Proplab Pro ray trace programs.