From: Paul Nicholson <vlf0403@abelian.org>
To: rsgb_lf_group@blacksheep.org
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Date: Fri, 16 Mar 2018 13:21:03 +0000
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Subject: Re: VLF: DK7FC > W1VD / K3SIW 8.27 kHz EbNaut - We don't give up!
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Here's an awk script to normalise the I/Q signal to the
RMS amplitude.

#!/usr/bin/awk -f

BEGIN{
    idx = 0;
    sum_square = 0
}
{
    stamp[idx] = $1
    ival[idx] = $2
    qval[idx] = $3

    sum_square += $2*$2 + $3*$3
    idx++

    if( idx == 300)
    {
       rms = sqrt( sum_square/idx)

       for( i = 0; i < idx; i++)
          printf( "%s %.5e %.5e\n", stamp[i], ival[i]/rms, qval[i]/rms)
       idx = 0;
       sum_square = 0
    }
}


Make sure the 'shebang' line is the first line of the script.

Save it in a file, say, iqnorm.

Make the file executable with: chmod +x iqnorm

Then pipe the raw ASCII signal through it, so that instead of

  vtwavex 26.wav | vtraw -oa | ebnaut -dp16K21A ...

you run

  vtwavex 26.wav | vtraw -oa | ./iqnorm | ebnaut -dp16K21A ...

I've run it on my recordings (sample rate 1Hz) of the 5char
transmissions and every single one has improved Eb/N0.

Not yet tried it on the W1VD, K3SIW files.

The '300' means 300 samples, so that's 300 * 0.45723950 ~= 137 seconds
for the W1VD files, or 231.5 seconds for K3SIW.

--
Paul Nicholson
--