Hi Stefan,
about your question:
Then i've done several tests using different frequency
tolerance values (above: t = 0.3 Hz). After calibrating the
soundcard by using the shown offset, the offset was 0,
consequencial ;-) But even if a tolerance of 0.002 Hz was
choosen, it still took
about the same time to get the first decode. Any
comments?
The reason is, the WOLF decoder processes an entire band
simultaneously. It's like having a bunch of receivers working in
parallel, each of them looking on its own frequency. This is the
reason why the CPU load from the decoder increases dramatically when
using a larger frequency tolerance.
Right now i feeld that i am missing a spectrogram which i can
show here. Just text! Odd.
One possibility to have a spectrogram-like display would be to
square the 'downconverted' (baseband) WOLF signal. The spectrum of
the squared signal should show distinct lines as already mentioned
by Markus.
I just wasn't aware of this when I wrote the graphic user interface
for Stewart's WOLF decoder.
In the normal spectrum, you will indeed hardly notice the WOLF
signal, which renders the display quite useless as the indicator for
the 'presence' of a signal. The trace gets invisible in the
spectrogram long before it drops below the level for successful
decoding.
All the best and good luck with the VLF tests, it's very
interesting. Especially when considering the possibilities with
GPS-based synchronisation (which, of course, does *not* exist in the
present implementations of the decoder).
Wolf DL4YHF .
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