Here is a simple tool for stacking FFT export files as a means to improve EbNaut decodes. 

Note that the start time offset for the EbNAut sequence must be the same for all recordings. For example, for a daily repeating EbNaut sequence, files from different days should have identical hour-minute timestamps (within a small fraction of the symbol duration). 

The files must be added in one by one. Calling
 add filename.txt
adds the contents from the specified file into an already existing file "sum.txt" which acts as an accumulator. This can also be accomplished by dragging the file icon over the add.exe icon. If sum.txt does not already exist, zero input will be assumed, i.e. the new file will be (weighted and) copied to sum.txt. The timestamp for sum.txt will be taken from the new file.

When using the commandline, a complex weighting factor can be specified as dB and phase, e.g.
 add filename.txt 6.02 90
will scale the new file by 6.02 dB and 90 (i.e. multiply by 2j) before adding it in. At the end, the program will output the number of bins, and rms averages of sum.txt before adding, the file being added, and the result after adding.

After adding all desired files, sum.txt can be converted to wav using
 ebnaut_ifft3a sum.txt
or drag-and drop, as usual.
