Re: WOLF: 135975 Hz, 10 b/s again

[Andy - KU4XR <ku4xr@yahoo.com>]

Thank you Markus for the explanation of WOLF modulation. I never stop learning.... a good thing....

Now looking for you as of 01:45 UTC 

 

Andy - KU4XR - EM75xr - Friendsville, TN. USA
Coordinates: N: 35º 43' 54" - W: 84º 3' 16"
http://lwca.org/grabbers/ku4xr/
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From: Markus Vester <markusvester@aol.com>
To: rsgb_lf_group@blacksheep.org
Sent: Friday, January 27, 2012 6:01 PM
Subject: Re: WOLF: 135975 Hz, 10 b/s again

Hi Andy, LF,

 

actually there is no carrier line in the WOLF spectrum, it's BPSK with a pseudorandom spreading code. In a spectrogram it resembles a 10 Hz wide noise band, which will be pretty much undetectable at any DX range. Actually a kind of spread spectrum mode, not unlike the GPS modulation (pssst ;-).

 

I think I have proven (and resolved) my soundcard phase-glitch problem. The attached trace shows a local audio test, with a WOLF signal generated on 1475 Hz. It is doubled in SpecLab's AM demodulator to regenereate a carrier at twice the frequency, which is phase compared to an hardware generated Rb-derived reference carrier. I have employed SpecLab's RDF mode to display phase as colour (retarding R-G-B-R). The first half shows the result from WOLF-Gui running on my "Grabber Notebook", which has a number of programs running. Besides the gradual phase roll due too a very minor frequency offset, there are jumps every few minutes. This is a bit nasty, as Wolf will still decode such a signal when it is strong, but not be able to go to its full sensitivity by using long coherent integration. The right half after 21:40 shows the practically perfect output from the Atom Netbook, the one which I have also used during several VLF transmissions. 

So, maybe it's worth another try. Will put the "good" WOLF signal on air a few minutes after 23 UT, QRG 135975 Hz, 10 b/s.

 

Best 73,

Markus (DF6NM)