Why don't voice radio communications use FM?

Mxsmanic schrieb:

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

Point is, stripped down and tweaked embedded versions are not "general
purpose" operating systems, but highly specialized ones which are
surprizingly reliable even if they are called Windows.

Stefan
(usually a declared Windows hater)

On Wed, 06 Sep 2006 22:50:20 GMT, "Grumman-581"
wrote:

"Steven P. McNicoll" wrote in message
link.net...
Didn't all early radio use AM?

Technically, they were probably digital... Dashes and dots... grin

.-.. .. ...- . / ..-. .- ... -
-.. .. . / -.-- --- ..- -. --.
.-.. . .- ...- . / .- / -.-. ..- - . / .-- .. -.. --- .--

----
--. .-. ..- -- -- .- -. ..... ---.. .---- .--.-. --. -- .- .. .-..
.-.-.- -.-. --- --


You're probably right but putting it into writing with dots & dashes
drives me mad!

After learning morse (up to 20 wpm) about 30 years before getting my
PPL it was easy to ident the VOR's. My instructor was very unhappy
that I would not write down the ID in dots & dashes. Claimed the
iexaminor would not like it. He couldn't believe I found it difficult
to understand morse written as you've done above. Just for fun I tried
to decode your characters, took me a 2-3 minutes to make sense of it.
Much easier to understand as a sequence of musincal type tones :-)

YOu don't want to talk about blech until you've had to change the cabin
airflow filter on a 727 in a cold hangar at 3 am with a hangover back in the
days when you could smoke on board the aircraft. Nicotine, for those of you
who haven't ever seen the raw stuff, mixed with all the rest of the crap
that had flowed through the airplane, strongly resembles drippy malted snot.

Jim




"Emily" wrote in message
. ..


Just kidding. Have you ever seen a coffee pot just pulled off an
airliner? Blech.

On 2006-09-06, Mxsmanic wrote:
Thomas Borchert writes:
Windows isn't Windows, as you try to make it in your generalization -
which in itslef implies a certain cluelessness with the topic.

Windows isn't Windows?

'Windows' is mainly a marketing name. There is a world of difference
between the Windows on GA GPS displays (it'll be the NT microkernel
running software designed by the display maker and will NOT contain the
Win32 subsystem nor the usual crufty device drivers) and Windows on a PC
(which does include the Win32 subsystem and a lot of other cruft).

It's the Win32 subsystem and various Windows drivers that people are
complaining about when they complain about the stability/quality of
Windows. Win32 itself is pretty vile - messy, looks like it was designed
by a dozen teams who never communicated with each other. Like car
crashes, most Windows crashes are caused by bad drivers.

A GA GPS display with the NT microkernel won't contain these buggy
drivers nor the hideous pile of cruft that is the Win32 subsystem. The
NT kernel itself is small and fairly elegant (even if the VMM, in my
opinion, leaves a lot to be desired). It's probably within the realm of
practicality to certify the NT kernel to a certain level of reliability.
(Whether it has been done or not I don't know).

--
Yes, the Reply-To email address is valid.
Oolite-Linux: an Elite tribute: http://oolite-linux.berlios.de

Dylan,

Like car
crashes, most Windows crashes are caused by bad drivers.


I like that ;-)

FWIW, for the PC space, most of the bad drivers are made by legions of
third-party hardware manufacturers. The fact that those legions exist
makes Windows and PCs so cheap and pervasive. It also leads to
problems. Which is why the hard- and software quasi-monopoly employed
by Apple does not have these stability problems as much. It also
explains the much lower marker share of Macs...

Oh, another point: The stability of the Windows PC OS has improved
dramatically with the last two or so versions.

But, as you say, all this is completely irrelevant to the "Windows"
used in avionics.


--
Thomas Borchert (EDDH)

Thomas Borchert writes:

That's all you have to offer?

If you have source, that's all you need.

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Dylan Smith writes:

'Windows' is mainly a marketing name. There is a world of difference
between the Windows on GA GPS displays (it'll be the NT microkernel
running software designed by the display maker and will NOT contain the
Win32 subsystem nor the usual crufty device drivers) and Windows on a PC
(which does include the Win32 subsystem and a lot of other cruft).

Even the NT kernel has never been validated or certified for any
safety-of-life use that I'm aware of. There's just too much code.

It's the Win32 subsystem and various Windows drivers that people are
complaining about when they complain about the stability/quality of
Windows. Win32 itself is pretty vile - messy, looks like it was designed
by a dozen teams who never communicated with each other.

It received an infusion of the very poorly written code from Windows
95 when NT 4.0 was written, from what I recall. It made the OS more
friendly, but less stable and secure. But apparently Microsoft felt
that was what the market wanted, and they were probably right, at
least with respect to desktop machines.

Like car crashes, most Windows crashes are caused by bad drivers.

Virtually all, not just most.

A GA GPS display with the NT microkernel won't contain these buggy
drivers nor the hideous pile of cruft that is the Win32 subsystem. The
NT kernel itself is small and fairly elegant (even if the VMM, in my
opinion, leaves a lot to be desired). It's probably within the realm of
practicality to certify the NT kernel to a certain level of reliability.
(Whether it has been done or not I don't know).

Avionics software is sometimes verified instruction-by-instruction in
its final binary form. I have a hard time believing that anyone would
do that for NT, even for just the kernel. Even a Linux or UNIX kernel
would be hard to verify.

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Thomas Borchert writes:

FWIW, for the PC space, most of the bad drivers are made by legions of
third-party hardware manufacturers. The fact that those legions exist
makes Windows and PCs so cheap and pervasive. It also leads to
problems. Which is why the hard- and software quasi-monopoly employed
by Apple does not have these stability problems as much. It also
explains the much lower marker share of Macs...

I find that companies that build nice hardware often build terrible
drivers, and vice versa. You end up having to find a compromise: a
vendor that produces reasonable hardware with reasonable drivers. If
stability is a priority, then you must settle for mediocre hardware
with good drivers; if features are a priority, you must settle for
bug-laden, system-crashing drivers with great hardware.

Oh, another point: The stability of the Windows PC OS has improved
dramatically with the last two or so versions.

Windows has been stable since NT was first released. NT 4
destabilized things a bit in its attempt to ape the features of
Windows 95.

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Dylan Smith wrote:
Like car crashes, most Windows crashes are caused by bad drivers.

The same is true of all operating systems; I once had a Sun Solaris system
crash because the tape driver had a bug.

It's been a while since I worked on any RTOS, but I seem to (probably
incorrectly) recall that applications running on VxWorks (the OS used on
the Mars Explorer, among other spacecraft) generally have full run of the
memory. That is, there is no distinction between the app and the OS as far
as access privileges to memory or I/O.

And I'll admit it eventually doesn't matter how reliable the OS is once it
passes a certain reasonable level, since the application(s) are always
going to be less reliable. If your app crashes, you may not get a "blue
screen" but the end result for the pilot is the same: they have to restart
the app somehow, and a cold restart is generally the easiest. (Though if
the OS is running okay it can tell when the app dies and do a warm restart
on the pilot's behalf.)

"Grumman-581" writes:

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

If they are stripped enough to be certifiably safe, they are not
longer Linux or Windows.

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