On Sat, 02 Sep 2006 20:19:15 +0200, Mxsmanic wrote:

Jim Logajan writes:

details snipped

Maybe someday the FAA and/or ICAO will consider replacing analog radios
with a more capable digital system....

All very interesting, but one of the criteria that any new system
would have to satisfy is that it would have to work in parallel with
the existing system. Adding features to the new system that are not
available in the old system would create dangerous differences between
the two. Seeing fancy displays in the ATC or tower for the lucky
digital users won't help deal with traffic from old AM users, and it
might even confuse things enough to cause problems.

A highly advanced solution would require replacing everything at once,
which isn't going to happen. A simpler solution that just provides
better quality audio could coexist with older systems without a
problem.

New systems (P25) already do this type of thing. I develop digital radio
systems. Police, fire, FBI, CIA, DoD, DoE, various municipal
utilities, and various branches of the military are all taking advantage
of this technology. In many cases, the old analog systems must co-exist
with the newer P25 systems. In some cases, more rural analog systems
actually connect with a P25 network via a specialized repeated.
Integration is not a problem.

Last I read, an FAA study indicated they need lots and lots of money
(sorry, don't remember the amount) to upgrade their infrastructure from
analog to digital. The sad thing is, it does not appear Congress is going
to give it to them. Worse, the same report indicates, over the next
10-years, the FAA will exceed their required conversion dollars by simply
maintaining and repair their existing, archaic, analog infrastructure. In
other words, the FAA needs to do something...even if they are simply
updating their existing analog infrastructure. Regardless, the money does
not appear to be available.

Advantages of this technology include:
o call queuing - meaning, PTT places you in a queue so you can get a word
in, even when the controllers are very busy. BTW, this also means no more
"walked on" transmissions.

o call prioritization - All sorts of cool things can be done here -
including, most recent exchange receives priority. Also, should IFR
traffic receive higher priority over that of VFR? What about commercial
traffic? Priority could be adjusted dynamically too. This means
planes in distress could be assigned higher priority. So on and so on...

o hang timer detection - a stuck PTT is not going to lock everyone out

o caller id - imagine your tail number, altimeter, heading, and aircraft
type provided to the controller on every PTT.

o MUCHO better frequency utilization

o Limited data services

The list could go on and on...needless to say, digital has some neat
features.

The only con of digitial compared to analog is reception. With analog,
you can hear a weak signal. It may sound like absoluete crap, but you can
still hear it. With digitial, either you have a strong enough signal to
hear it...and it sounds awesome...or you hear absoluetely nothing at all.

Greg