Greg Copeland writes:

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.

So why wouldn't it extend to aviation?

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.

They need not upgrade it all at once.

The sad thing is, it does not appear Congress is going
to give it to them.

Congress, like most of America, is hysterical about imaginary human
threats these days, and has probably lost track of the much more
mundane but much more serious safety risks associated with
infrastructure, aircraft, and crews.

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.

Do other aircraft hear the transmission when you make it, or when the
controller hears it? Granted, they are only supposed to listen to the
controller, but in practice they will be listening to other aircraft
as well.

How do you make this work in parallel with analog systems that cannot
queue?

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...

It's best not to jump off the deep end with gadgets. Just because
something can be done doesn't mean that it should be done.

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

Where does this leave people with analog equipment?

o Limited data services

What kind of data services do pilots need? Are they going to be
surfing the Web?

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

Neat features aren't necessarily desirable features. There is too
much of a tendency to bloat digital systems with features that have
been hastily designed, inadequately analyzed, and barely tested at
all.

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.

If the digital threshold is set where the threshold of intelligibility
would be in analog, there's no net loss.

--
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