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Re: LF: RE: Progress using WOLF on VLF

To: [email protected]
Subject: Re: LF: RE: Progress using WOLF on VLF
From: Stefan Schäfer <[email protected]>
Date: Thu, 02 Feb 2012 19:54:46 +0100
In-reply-to: <[email protected]>
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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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