BillJ wrote:

I have a Monroy ATD200 like new. Does a good job in keeping you alert in
busy areas.

I don't agree. I've flown a plane with a Monroy in busy airspace
(under a class B shelf with lots of surrounding GA fields) and its
nearly constant alarms made in next to useless. On the other hand, I
thought it worked great out in less populated areas, particularly
around VORs and other places in the sticks where airplanes tend to
meet.

The best TCAS-like solution I've seen for busy areas is the radar
traffic (TIS) data available with a Mode/S transponder. The only
drawback is that you have to pony up for the Mode/S transponder and a
compatible display device. Still a lot cheaper that an actual TCAS.

John Galban=====N4BQ (PA28-180)