Hi Stefan,
Integrate WOLF in SpecLab - too much overkill. The program (SL) is,
imo, already too overloaded with functions as it grew over the
years. Maybe, after everything inside SL uses GPS-based timestamps
(like Paul Nicholson's VLF RX Tools), there will be a simple
interface to feed the resampled audio stream (which would then have
*exactly* 24000, 32000, or 48000 samples / second plus a timestamp
for each sample with an accuracy in the microsecond range) towards
other programs, using a TCP/IP based method, or a shared memory
buffer (as in Paul's VLF RX Toolchain). THEN, after all that being
finished, the WOLF GUI would be one of the first external
applications which would make use of the system described above.
Together with Paul I am currently comparing different algorithms for
the resampling / interpolation. Some of them look attractive and
simple on first glance, but give too much phase noise when one gets
closer to the Nyquist frequency. But details about that would be way
off-topic here.
All the best,
Wolf DL4YHF .
Am 02.02.2012 19:54, schrieb Stefan Schäfer:
Hi Wolf,
Thank you.
And what about WOLF included within SpecLab? This would help a
lot,
regarding the drift and offset compensation, especially for the
receive
stations. Do you think it could be implemented into the digimode
terminal?
73, Stefan
Am 02.02.2012 19:13, schrieb wolf_dl4yhf:
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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