>Does anyone have a working example of the IIR filter block in GNU
>Radio Companion that I can see, and the filter designer app, table, or
>equation which generated the coefficients?
Could you try grc files attached in http://lists.gnu.org/archive/html/discuss-gnuradio/2012-08/msg00128.html. I think those were tested with gnuradio-3.6.1.
You can either use gr_filter_design tool (new version) or scipy functions (scipy.signal.iirdesign/scipy.signal.iirfilter) for designing IIR filters.
>Negating A coeffs doesn't appear fix
the issue in either case.
To know more about the negation of "a coeffs" please follow this thread: http://www.ruby-forum.com/topic/4408052.
-Sreeraj