"Thomas Borchert" wrote in message
...

Clearly, you haven't flown with the unit. This statement couldn't be
more wrong. The antenna characteristics are such that traffic being
more than 1500 or 2000 feet different in altitude will not be
annunciated. Altitude has NEVER be a problem for us in actual
operation.

It *has* to be affected by the limits imposed by positioning in the
particular aircraft, internal antenna vs external, etc.

My experience varies with yours. I get alerts often from flight level
traffic I never see, and I get some alerts from same altitude traffic so
late it worries me.