I got some time on a vehicle with a metal roof and set it up with a set of VHF antennas.  Tuning in on NOAA weather radio on 162.400 MHz from a fixed location there was a stable heading reading albeit with a low signal quality.  In urban driving the audio Doppler tone revealed quite a bit of multipath.  When in a less congested area good quality readings were observed.  On to calibrating and turning the arbitrary heading into useful information.