Collision avoidance equipment

samcapt wrote:
I have been reading about several low cost alternatives which provide
collision avoidance from Aviation Consumer. These devices seem to give
a rough estimate of range and the seperation altitude, but not
direction. Does anyone know of a portable system that give direction as
well?

No, that would be rather difficult. These devices listen
omnidirectionally for other aircraft's Mode C returns. The
built in units use multiple directional antennas to do this
which would require a very large portable unit or precise
setting of the remote antennas neither of which was practical.

What might be possible is to sniff the TIS signal off a mode
S datalink (provided there is a mode S transponder somewhere
nearby), but I don't know enough about how that works.