This directory contains a continuous record of the reception of
of the 24 KHz (VLF) carrier signal from NAA (Cutler, ME) at Moore Observatory
in Brownsboro, KY (38 20' 40" N, 85 31' 44" W).

Archival files are indexed by year. 


The receiver hardware and electronics have hardly been altered since collection
began in 1999.  The digital processing has evolved of course, and would be
obvious from changes in the appearance of the  plots.  Some of these changes
resulted in gain and zero-point shifts which would have to be taken into account
in a comprehensive analysis of the database.

The most recent change was on February 27, 2019, when we modified the
processing pipeline while maintaining the same hardware.  On and after that date
the plots are stored as png rather than jpg files and have better quality.

The data are available as a public resource.  If you use these data in a
scientific publication, we would appreciate acknowledgement.  For more
information than we provide here on line, contact kielkopf at louisville dot edu.