Re: [Discuss-gnuradio] filter ssb

[mike revnell]

Chuck Swiger wrote:

> At 10:34 AM 1/6/2006 -0700, you wrote:
>
> > In continuing efforts to learn how to use gnuradio and the USRP I've 
> > continued banging on the code I posted previously.
> >
> > Extending the length of the ssb demod filter scheme to 1023 taps 
> > seems to make it useful, at least for listening in on the ham bands. 
> > I've also added AM demod using the complex modulus block.
> >
> > AGC is a far richer field than I ever imagined. There are ever so 
> > many parameters to tweak.
> >
> > The attached tarball includes a reasonably functional and complete HF 
> > radio.
> >
> > If deemed suitable for examples it may be included there.
> >
> > I don't have a web site to put it up on but if anyone else has such 
> > be my guest.
>
> Mike - I love it!  Your most recent attachment with complete gui was
> just added to cvs gnuradio-examples/python/aps/hf_radio/
>
> --Chuck
Glad to hear it.

In the interest of full disclosure I note the following.

In poking around some more on the net I've learned that the basic 
approach is known in the literature as the Hartley image-reject 
receiver. In this instance the I and Q channel mixers are in the DDC in 
the USRP. The low-pass filters and hilbert transformer are implemented 
in the translating filter. As noted in my writeups in the files the 
hilbert transformer is implemented as a complex pair with 45 degrees 
each rather than the more usual hilbert transformer with matching delay.