Thomas Borchert wrote in message
I hate repeating myself, but I simply cannot imagine a likely scenario
where two Mode C equipped aircraft fly close enough together to be a
collision threat and one is interrogated while the other is not.


Have you flown yet with the ATD300? The altitude and range vary
wildly, and I do mean all over the place. It would display 5 miles to
2 miles then 4 miles then 0 miles while the altitude would bounce
between 4 or 5 different levels some as many as 10,000 feet in
difference all within a couple of seconds. I would see this kind of
completely erratic display almost the entire time. For brief period
it would show a voltage readout, then back to a wild display of
traffic. I don't see how any aircraft can go from 0 miles to 4 miles
or 25,000 to 800 in 1.5 seconds. The ATD300 is small in size, but I
have no confidence in what it tells me. The 200 performed way better
performance wise, but that one had no altitude. I think the 300 is a
good voltage meter, but as for traffic, no way.