After reading of the recent mid-air out West I bought a Zaon MRX PCAS
(Portable Collision Avoidance System) from Aircraft Spruce &
Speciality to try out. I also fly a Piper Vagabond without an
electrical system and this unit doesn't require your aircraft have a
mode C transponder as it's a passive system using the Mode C readout
from another airplane. The unit has a build in electronic altimeter
which compares the Mode C readout of the "target" a/c and gives you a
"relative" altitude difference and approxiamate range. I used it
locally on the ground and observed the readout of a Piper Cherokee
on downwind at the local airport..turn base and
final........amazing!!! Although this unit doesn't give you a bearing
to the target it does give you the altitude and range which sure gives
you some warning. They have a web site http:zaonflight.com which has
an online manual, etc.

Noel Anderson
Schweizer 1-26E