Spektrum,
Thanks, its a sad reality that anyone and everyone who discusses or provides
an intelligent analysis of an accident results in getting personal attacks
from those who rarely post anything intelligent but 2 or 3 line inordinary posts.
FACTS
A-DSB signals for the C-130 were in this case continuous.
There is no evidence of "patchy" or "unreliable signals" involving this C-130.
Most A-DSB signals above 10,000 feet can be seen continuously across most continents.
Even at 6,000 feet, A-DSB is seen continuously over most of Australian flight routes.
Public Internet sites - refer primarily to flight aware, which takes feeds
from anyone and everyone that provides far more than that received by
official ground receivers.
If you provide such a feed, then you get to see all the hidden "blocked" information
that you cannot see on flight aware public site. You get to have your own
IP address that you can share with others to see all that info.
Now, I happen to be one of those "feeders" and together with other "feeders" we get
to see 'the big picture" and rarely do signals at altitude drop out unless typically
at the extreme end of the range say 200 to 300 NM at 35,000 feet depending on location, height and antenna.
Your own A-DSB feeder will have "blind spots" such as directly overhead, or blocked by the location of either
your antenna or the aircraft antenna or a combination thereof. But, because each aircraft is received by
multiple receivers, the odds of all receivers not receiving the signal is generally, entirely remote.
150 miles at 6,000 feet is a no-brainer and odds are that at 6,000 feet where this C-130 broke up, that
there were a significant number of receivers monitoring the A-DSB out.
This brings in an increase in accuracy to the point of indicating
altitude and airspeed. Its called M-LAT, meaning multiple stations increase accuracy of data interpreted.
That's why its vitally important to enter your exact location and the height of your A-DSB antenna to enable
the MLAT accuracy.
Yes, this accident happened "miles away" but 1090 Mhz Signals go a very long way at 6,000 feet and
odds are it could be seen as far afield as Albury, Canberra and Sydney let alone
the hundreds of private receivers who feed data into the system.
Another good reason why A-DSB in and out was adopted and why 406 mhz beacons
should be in every aircraft regardless of size.