[SADXA] Eclipse at 10 MHz

[Darrel]

I monitored WWV at 10 MHz during the entire UTC day.  In the plot below, 
the red line is the signal amplitude, the black line the received 
frequency offset from the Doppler shift on the 10 MHz caused by motions 
in the ionosphere.  The receiver was the Grape v1 from the HamSci 
project (made by KB7NIE), with a modified version of fldigi as the 
software, running in a Raspberry Pi.



Above, the strength (red line, right vertical axis) and frequency offset 
(black line, left vertical axis) of WWV at 10 MHz during the UTC day.  
The strength of WWV dropped at about the time of the eclipse around 18h 
UTC, but stayed down for a couple of hours more, beyond the end of the 
eclipse.  Note the sudden drop in signal strength around 4:30 UTC, and 
the corresponding jump back around 13h UTC.  That's caused by the MUF 
dropping below 10 MHz, which happens every day and is nothing to do with 
the eclipse.  The Doppler shift during the day was about +/- 1 Hz peak.  
The frequency standard for the receiver was a Bodnar GPS-locked 
reference, with any error many orders of magnitude below the observed 
frequency offsets.

    The antenna for these observations was a 10 MHz interferometer, 
phased to give a null towards WWVH and a simultaneous peak towards WWV.  
WWVH can be stronger than WWV here at some times of the day, without a 
directional antenna.



As a comparison, above is the X-ray data from the GOES-16 and GOES-18 
satellites. The X-ray data look complicated.  I presume the event at 5h 
on GOES-16 (in red) is the earth getting in the way of the sun as seen 
from GOES, with the moon getting in the way 12 hours later, but there 
was a moderate C-class solar flare happening at about the same time as 
the eclipse.

Cheers,
     Darrel aa7fv.