DOI: 10.5281/zenodo.11075267
title: W0TBR April 2024 Eclipse WWV Doppler Shift

description: April 2024 Solar Eclipse Data via W0TBR

W0TBR recorded Doppler drift of 15MHz WWV/WWVH carrier signals prior to and subsequent to the April 8 2024 solar eclipse.

Although the W0TBR station was not in the direct path of the solar eclipse - with about only 33% occlusion at maximum shadow - the Doppler shift was recorded to determine any effect as compared to other shifts to be recorded within the direct eclipse path or within the midpoint of the signal path between WWV/WWVH and the recording station.

W0TBR is located in Grid CN85qn - Lat. 45.555N & Lon. 122.623W at an elevation of 68.5m ASL.

Antenna used is dual band inverted V fan dipole resonant on 20 and 17 meters with an apex at 10 meters above average terrain and tuned for max signal at 15MHz.

Antenna feed is terminated at each end with 1:1 balun to minimize noise and non-resonant effects.

Radio used is a Flex 1500 SDR stabilized with a 10MHz OCXO. Radio was tuned to 14.999MHz USB with AGC deactivated and RF gain fixed at value of 45/100.

Received +/- 1kHz signal was directly fed through Conexant audio chip of HP 600G3 computer into Spectrum Lab (SpecLab) software.

SpecLab (V 2.99 b15) was configured similar to that used by WA9VNJ for the 2017 solar eclipse recordings: 512K FFTs with 75% overlap resulting in readings every 12 seconds.

SpecLab time, peak frequency and amplitude data were recorded from 0143 UTC to 2359 UTC on April 08 2024 and saved to a text file.

Screen shots of the frequency shifts (+/- 3Hz) were taken each two hours for a total of six hours around the local maximum solar shadow which began about 1733 UTC, peaked at about 1825 UTC and ended about 1919 UTC. Note that the original SpecLab screenshots are in vertical time orientation; in order to provide a comparable view where time is on the horizontal axis the views are inverted and ‘stitched’ together for the final view’s full six hour period.
description: Initial Observations

Local sunrise Doppler shift (likely WWVH and/or multipath) at about 1630 UTC appeared more ‘diaphanous’ than other days; eclipse shadow began at about 1635 UTC in Kauai, Hawaii; at about 1735 UTC the principal signal (likely WWV) begins to drop in frequency and remains negative (below 1KHz) until about 1830 UTC when it crosses into positive Doppler shift where it remains until just after 1945 UTC when it exhibits less differential - apart from a negative excursion (WWVH and/or multipath?) and some instability through 2145 UTC.

The “classic” eclipse frequency excursions recorded are less than 1 Hertz but nonetheless discernible as compared to those recorded by others closer to the path of the eclipse.

Also, due to W0TBR’s distance between WWV and WWVH (1,524km vs 4,234km respectively) it is difficult at present to separate the carrier signals and their respective shifts due to the variable effects of the ionosphere via the eclipse.

Finally, the westernmost WWVH location at Kauai began in solar shadow at about 1635 UTC, peaked at about 1713 UTC and ended at about 1800 UTC. The Ft. Collins, CO WWV location began in shadow at 1730 UTC, peaked at 1841 UTC and ended about 1930 UTC.  The peak frequency and amplitude data are most likely for WWV; the screen shots provide greater visual detail of the ionospheric behavior surrounding those peak values.

 

DATA FILES

SpecLab data text file - recorded peak frequency and amplitude 0143 UTC to 2359 UTC

 

SpecLab 2 hour screen shots - original & inverted

 

SpecLab six hour continuous screen shot (inverted)

1545 to 2145 UTC

 

SUGGESTIONS FOR IMPROVEMENT APPRECIATED!