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Attached is a little 24 hour plot of NAA 24
kHz, versus the local noise floor on 29.5 kHz (note that there is an offset
between the two due to the antenna bandpass filter favouring 29
kHz, NAA would really be higher above the noise in 1 Hz).
Interestingly the night-to-day level difference is
only very few dB between midnight (3 UT) and midday (15 UT) over
the Atlantic. It is almost compensated for by the decreased background
noise, especially during the late morning hours. Bob actually left a
couple of discernible pixels when he stayed
on after our local sunrise: http://df6nm.de/vlf/vlfgrabber.htm
Best 73,
Markus (DF6NM)
PS. I've split the spectrogram in case
Dex would show up again on 29.501 kHz.
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