Why don't voice radio communications use FM?

Greg Copeland writes:

The repeater initiates the call on your behalf. The repeater is queued
rather than the analog radio. Likewise, the reply goes to the repeater,
which then re-RXs ("repeats") as analog. For this to work, the analog and
digitial systems must have their own frequencies.

Is there a guarantee that transmissions will occur within a certain
period? Are these systems verified for safety-of-life applications?

Also, the concept of "emergency" call is also very useful. For example,
it places you at the top of the queue. Combine "emergency" with a GPS
source, plus data services, and now your squawking 7700, your GPS position
is sent with your PTT, and you now have priority with the controller.

Interesting.

This does bring to mind something else, though: If your channels are
so crowded that you need a system to queue messages and give priority
for emergencies, you need more channels. It's much safer to have
multiple channels that don't require queuing than it is to queue on a
single channel.

Also, how do you deal with analog users who have no queuing? They
will still walk over the simultaneous transmissions in digital and
analog.

An anachronism? No worse off than they are today.

Actually they would be, since practices extended to digital users
would naturally tend to affect analog users, even though they don't
have the same advantages. This would put them at a safety risk.

Until everyone
is converted, such features would simply be a perk to controllers; with
the potential to increase QoS for those that digitally participate.

Quality of service has to translate to increased safety in my book.
As I've said, if fancy queuing systems are required just to manage
traffic on the channel, then there are not enough channels, digital or
otherwise.

Oh, most definiately not web browsing. TAFs, METARS, in route weather,
PIREPs, TFRs, ATIS, ASOS, TWEB, NAV IDs, etc...

As long as someone is still actually flying the plane. A beautiful
digital display of weather 300 nm ahead doesn't help if it distracts
you from the mountainside looming just ahead through the cockpit
window.

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