This could explain the behavior in regards to the altitude with the
Monroy unit, which does not use any altimeters.

http://www.surecheck.net/avionics/altimeter.html

I think it was the Ryan series of tcas that when first launched only
used altitude from the "host" transponder, rather than directly from
the encoder, and found it was not a 100% reliable way to get altitude.
The squawk code apparently is the major problem, and with no "second
opinion" from an additional altimeter, I can see how the Monroy unit
might get confused.





(FISHnFLY) wrote in message . com...
"A lot" being + 300 for about 1 seconds then - 600 for another half
second to +700 then it will stick for a while, only to go back to very
odd changes. If I read this right I would have had 60 aircraft around
me between 5 to 0 miles and one at just about every altitude.
Occasionally it will resort to showing what appears to be actual
altitude, but I can't tell for sure when it switches. My overall
opinion is that it doesn't seem to be able to "lock" onto any one
particular aircraft, but instead will swing between many, or be
misreading them all together. I flew with it again this evening and
it did basically the same thing, only this time I had a low wing piper
pass directly above me, not more than 100 to 200 feet, and it kept
telling me someone was way below me at "0 NM to 3 NM"

I am starting to think that the ATD-300 is still in a "beta-test"
mode, and perhaps not ready for prime time. I got one of these right
out of the release along with three other guys, and we have all had
about the same results. I am considering trying their competitor
trafficscope while I still have the ATD to see side by side for myself
how they compare in accuracy. I was going to get another competitor
called proxalrt into the ring as well, but the only place that carried
it said they don't keep it in stock.

We'll see.