Re: [Discuss-gnuradio] SSB demodulation

[Johnathan Corgan]

cswiger wrote:

> > > Hi All - I'm making wild stabs are writing modules to demod SSB
> > > with REAL+IMAG or REAL-IMAG for upper and lower sideband, simply
> > > by cloning David Carr's gr_complex_mag module:
> John - that's for the comments, always appreciated.  I'm simply
> working with the fm radio code, replacing gr.quadrature_demod_cf

My point was that your algorithm for SSB demodulation is incorrect--it's 
not simply a matter of adding (or subtracting) the real and imaginary 
portions of the complex symbol stream.  The math is a bit complicated, 
but in the end you have apply a 90 deg. phase delay to the imaginary 
portion first, via what's called a Hilbert transform.

It sounds like you think the frequency translation already provides the 
90 deg. phase shift--there is one involved there but it is something 
completely unrelated.

I'm actually not all that familiar with the guts of the GNUradio code 
base, so I can't tell you how to do this.  Eric posted a reply with some 
routines you can use, I think.

73 de Johnathan, AE6HO