Dear LF/VLF group,
In my 10th experiment i did a CW transmission test on 8970 Hz / 33km,
arround 11 UTC. No one in some 10 km radius received the signal but my
grabber PC was recording the whole day. Now i successfully extracted the
part of the CW transmission which is just some minutes.
The CW (somewhat arround 100 bpm) signal was converted to 700 Hz using
SpecLab: A 10th order butterworth filter (BW= 3 kHz, f center = 8970 Hz)
was applied. After that the clipper and noise blanker was applied. Then,
frequency conversion by 8270 Hz (USB downconverter). After that a very
narrow CW filter (all within SpecLab), centered at 680 Hz, 100 Hz BW and
50 Hz slope was applied. This strongly improved the audibility and
removed unwanted tones.
It is the first detection of a real CW transmission on the Dreamers
Band / 8970 Hz in the far field and even above 1 Lambda. The distance is
40.0 km
An audio file is available at
http://dl.dropbox.com/u/19882028/DK7FCinCWon8970Hzthe33kmband.WAV (about 40 MB)
The message was invented spontaneously. If i would have known that it so well
audible, i would have been better prepared, HI.
Vy 73, Stefan/DK7FC
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