After rewriting my code to be less sensitive to blocking everything is working.  I broke up the processing in signal acquisition, number crunching and display which is much simpler than keeping all that going at the same time.  For signal acquisition I am experimenting with sample size less than a full revolution of the antenna to keep update times reasonable.  

Now that I have a compass sensor working I wonder if I can improve on the +/- 1 ° or so from the compass by using GPS when in motion.  The GPS "course over ground" which when in motion gives direction based on position differences could be more accurate.  Ideally I could switch navigation source.

I have been using "RDFMapper"  which displays a google map and take GPS and RDF input several ways based on settings.  It draws a bearing line from the location of the direction finder which can be relative to the direction of the vehicle or a fixed specified angle from north.