[time-nuts] First results of eclipse data recording

John Ackermann N8UR jra at febo.com
Sun Aug 27 11:20:54 EDT 2017

(This is more amplitude than frequency related, but thought it might be 
interesting to the group.  If not, sorry for the intrusion.)

I used three software defined radios to record just under 1 TB of data 
during the eclipse period from my cottage at Beaver Island, Michigan, 
over 8 hours from 1400 to 2200 UTC.  Frequencies recorded included the 
entire AM broadcast band and four ham radio bands, one of which also 
covers WWV at 10 MHz.  (Obligatory time-nuts/FMT-nuts: the receivers 
were either locked to an FTS4100 cesium standard, or had reference 
markers derived from it.)

It's taken a few days just to aggregate and back up the data.  Last 
night I was able to do the first actual processing.

This initial result is a "spectrum movie" showing the AM broadcast band 
from 0.500 to 2.00 MHz over the 8 hour test period, recorded by a Red 
Pitaya SDR at 2.5 megasamples/second.  It will take more work to 
separate noise/spurs from real signals but it does look like carriers 
came up out of the noise during/after the eclipse period.

The movie was created with a Gnuradio script reading the recorded data 
and displaying an FFT plot, which was captured with a screenshot tool 
every five seconds.  I then turned the images into an .mp4 movie at 30 
frames per second, so the 8 hour period runs by in a bit over 3 minutes. 
  I used a deep FFT (8192 points) with long averaging to get rid of as 
much of the crud as possible.

Blog post with some details here: http://blog.febo.com/wp/?p=202

Get directly to the movie on YouTube here: https://youtu.be/bqRhfCiD8Pw

There's lot more analysis to be done, but I thought this was a necessary 
(and interesting) first step.


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