Andrew Gideon wrote:
I don't understand the relationship between VDL, Mode S squitter, and
UAT. My cursory reading tells me that these are three different
communication technologies, any of which can be used to carry ADS-B data.
However, that would appear to defeat a major benefit of ADS-B: if two
aircraft are out of RADAR coverage, they're still supposed to "talk" to
each other. But if one is carrying a UAT and another a Mode S squitter,
how could that communication occur?

Nope, you understand just fine. [It's the FAA that seems to be having
trouble.]

Right now you have three major companies, all lobbying for a different
communications means. The FAA is under political pressure from the
airlines to fit it into Mode-S because they had Mode-S datalink rammed
down their throats already. Personally, I think VDL is the right
choice, but I have to admit tht it seems to be the underdog.
Regardless, I hope they DO make a real decision (instead of relying on
TIS-B to make up the interconnect and letting them all compete
nationwide - that's just dumb).

Which means I could buy the Garmin GDL-90 and find it useless? That's not
something Garmin is advertising.

Look how many folks have bought the Garmin 330 for TIS, and now the
stations are already starting to go away.

BTW, the latest edition of AVIONICS Magazine had some pretty good
articles in it on ADS-B.
Is that:
http://www.avionicsmagazine.com/
? Is the article there? I'm not seeing it (at least in the June edition,
which is the latest I see online).

Right magazine, wrong month. The July edition landed on my desk in the
last couple of weeks.