Surecheck TrafficScope Pirep?

(MikeremlaP) wrote in
:

I haven't taken ours apart, but I've heard the same from another guy
who took his apart - no detector, correct?

No megabit data slicer. It receives the transponder reply, but does not
turn it into a digital datastream.

The ATD-200 uses two schemes for altitude discrimination: signal
aperture ratio and Mode C LSB comparison. The signal aperture ratio is
the dominant factor for traffic with no Mode C.
+++++++++++++++++++++++++++++++++++++

If I understand him correctly (from this and other correspondence) he
IS somehow detecting altitude info and the unit is supposed to ignore
hits above/below 2500' of your altitude.

The "aperture ratio" thing is actually kind of clever. Basically it
looks at how LONG the signal is to decide if it's real (transponder) or
not. Simple (and obvious, once you think of it). But earlier attempts
didn't do it and the results was so many false alarms that they were
almost unusable.

How this relates to altitude? Hmmm... sounds a bit strange.
"...traffic with no Mode C"? Frankly, I have no idea how that would
relate. No idea at all.

As for the LSB (least significant bit) that also doesn't quite make
sense. First off is the question of whether it even SEES the LSB (I
personally do not think that it does). But even if it did, comparing
the grey code LSB between your xpndr and a received one tells you
nothing (other than your altitudes are not exactly equal). You two
could be 100 feet off, right on a transition level for the bit, and the
bits would be different. Or (I need to look, but I think the most
significant digits are last) you could be 10,000' apart and have the
same LSB.

I noticed after our unit came back from being revised that the SUPR
LED often lights up a lot in the Phoenix area, but no Traffic Alert.
I took that to mean the unit was picking up the Air Transports as it
used to, but now "suppressing" their Traffic Alert since they were out
of bounds based on Mode C info.

I've never seen the SUPR LED come on by itself. Curious. I *have* seen
it go on and off semi-randomly while tracking what is obviously the same
signal.

I can try your test and test my theory by turning off our Mode C and
seeing if suddenly I start getting Traffic Alerts on everyone.

Let me know. I have NEVER seen ANY difference in terms of traffic
alerts regardless of whether my transponder is on or off.
- - -

In one sense the unit performs however well it performs, regardless of
how. Frankly, I have been surprised by the reluctance of the mfr. to
answer this one simple issue. [We are *not* asking for a big trade
secret here. G]

A while back a similar thread came up on another list. I sent Monroy an
e:mail, which was never answered. I later sent another, I felt nicely
worded, but asking if they actually decoded the address. I got a reply
that the unit "formed a cone of protection around your aircraft..."
Basically what was in the advertising.

So eventually, some weeks later, I called. I really feel that I was
very polite. I explained that I owned one of the units and that found
it useful. But that sometimes I got "hits" that were obviously from
aircraft far outside of the implied range. I also explained that there
was some considerable confusion among the users I know as to whether or
not the unit actually decoded and compared the altitude of the two
transponders. Could he resolve the issue by telling me if the unit
actually DID look at the transmitted altitude.

He hung up on me.

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James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
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