Date: Sat, 27 Nov 2004 12:05:54 -0500
From: DL4YHF@aol.com
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: MSK etc and stability
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Greetings all,


Alberto 
>>> Firstly, I like the idea of Andy, of a GSPSK (Gentle Sloping PSK),
 which should substantially reduce the amplitude variations of the signal, when subject to phase
modulation. Any volunteer for a mathematical analysis (or a simulation) of the crest factor as a function of the "gentleness" of the phase transitions ?
<<<

And, since my maths is a bit rusted, which phase slope would be the "best" (if it's that easy at all) ? At the moment I only used a linear ramp, so the "GPSK"'s phase looks like a trapezoid on a phase plot.. by something tells me a raised cosine would produce less sidebands. (Furthermore, the unwanted sidebands are still much stronger than for a PSK31-signal with its nice amplitude shaping). 

Anyway, I still didn't give up the idea of MSK or even GMSK. There are some novel implementations of this around which I still have to dig through, like this one (tnx SM6LKM):

www.ee.surrey.ac.uk/SSC/CSER/UOSAT/papers/icdsc_ws/icdsc_ws.html (look for the "Coherent MSK Experiment", and for the author's conclusion). 

I wouldn't say the Hodgart-Massey decoder is simple, but it seems to have some interesting properties (especially the fast acquisition time) which may be beneficial for LF.


Regards,
Wolf DL4YHF.