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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Jim Logajan writes:

Just tell people they would operate it like a telephone: the pilot would
direct her call to a particular listener (e.g. ATC) and ATC gets a signal
(like a phone ringing!) and can let it ring until they have time to answer
the call. But in a pinch, the system could also act like a party line system
and after hitting the emergency transmit button in her aircraft, the pilot's
distress call would automatically cut in over less-urgent calls to not only
ATC, but to any aircraft who have set their receivers to automatically accept
emergency calls.

In essence, digital systems provide multiple virtual private circuits if
needed, but still allow broadcast or "party" line equivalents for situations
where that communication mode is more useful.

What about analog users? What if an analog user transmits while a
queued message is being transmitted?

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Jose writes:

"Your call is important to us. Our operators are busy right now giving
their full attention to other airlines. We will be with you shortly.
Did you know that you can find most of the information you seek on our
website? Please log on to www.getlostspamcan.com. In the mean time, we
hope you enjoy our new rap hold music."

"If this is an emergency, press one. If this is a normal call, press
two. If this is a reply to a previous call directed to you, press
three.

If the emergency prevents you from maintaining your assigned altitude,
press one. If it prevents you from maintaining your assigned heading,
press two. If explosive decompression has occurred, press three. If
both pilots are unconscious, press four. If the aircraft has exploded
in midair, press five. If you have struck a mountainside or structure
while waiting for the queued reply to your last call, press six. If
none of these apply, please stand by, and a controller will personally
address your emergency as soon as possible. The current queue is ...
seven ... minutes long. Thank you for waiting.

High fashion reigns at Frammis Terminal's Duty Free Mall, with fall
colors now in stock! Reserve your table via pilot radio at the
Fallingsky lounge for fine dining after touchdown!

The current queue is ... six ... minutes long. Thank you for
waiting."

--
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"Mxsmanic" wrote in message
...

SNIP


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.


If you're flying something that requires you to be concerned (near term)
with Wx that is 300nm ahead...and you are low enough to hit something that
is part of Earth...you've got larger issues to deal with than how you are
communicating.

;O)

Jay B

On Sat, 02 Sep 2006 16:58:12 GMT, "Steven P. McNicoll"
wrote:


"Ron Natalie" wrote in message
om...

No actually, it's just historical. Early av radio used AM, and for that
reason we still do.


Didn't all early radio use AM?

Nope. Used Morse code.
You didn't mean quite that early?




Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

"Bob Noel" wrote in message
...
Which systems? entertainment system? coffee pot? weather display? PFD?

I'm not sure which ones were on what type of embedded system since I was
only up there for a 6 month contract and didn't really get much experience
in what all the other groups were doing... Basically my own niche, for the
most part, but I was aware of them using various types of embedded O/Ss for
different things... The portion that I was working on was an embedded Linux
platform... Embedded WinCE was used for some other things and embedded XP
was used for other things... Sorry I can't be more specific, but I really
didn't get a chance to see everything that they were doing up there... What
I did get a chance to see was pretty neat though... Enough to reinforce to
me that if you have the money, someone has a way for you to spend it...

"Emily" wrote in message
. ..
Hey, the coffee pot's important.

I believe that there are some software controls for the coffee pot... On one
of the aircraft that I was reading the docs on, there were software controls
for various operations and measurements of the waste water system... I don't
remember there being a way of initiating a comode flush via software
though...

"Mxsmanic" wrote in message
...
I do. Linux has the same problems for safety-of-life applications as
Windows. All general-purpose operating systems have the same
problems.

The embedded flavors of Linux that you see on aircraft systems are
*extremely* stripped down... Same with the embedded flavors of WinCE and
WinXP...

"Mxsmanic" wrote in message
...
Nothing that runs a Windows OS is suitable for safety-of-life
applications. This is no reflection on Windows; it's just that the
operating system is designed for general information processing use in
homes, offices, and schools ... not for process control, real-time
systems, or mission-critical applications.

Sorry, but you're not quite familiar with the embedded versions of the O/Ss,
so you really can't make that sort of statement with any kind of
certainty... The embedded versions are a completely different beast than the
consumer versions... I might not like Windows, but at least I recognize that
there is a difference between the embedded stuff and the consumer stuff...

Mxsmanic,

Sources?

Yes.


That's all you have to offer?

--
Thomas Borchert (EDDH)