On Apr 19, 9:49 am, Kev wrote:

Why are so many things abbreviated in NOTAMs and other similar documents?

They're referred to as NOTAM Contractions:

https://www.notams.jcs.mil/downloads/contractions.pdf

Even words that aren't very long to begin with are often abbreviated, saving
only a letter or two.

How foolish it must seem.

I can't think of any situation today in which bandwidth
would be so severely limited that saving a letter or two would make a
difference,

Not being in the loop limits scope to thought.

so I assume

I don't

there is some historical reason for the abbreviations.

There are still several systems still operating in the NAS with low
bandwidth, low storage capacity and running legacy software. The NAS
world doesn't begin/end the Internet, high bandwidth, high capacity
storage, that many take for granted.

There are many I've never seen or read about... or care to... (read:
The novelty of testing the 6V6 at the Radio Shack when I was a kid,
has long since worn off)

But I know of several systems running on machine decades old.

Last I was working with it (~'93), the AWPs were running old Tandem
(Fault Tolerant) hardware.

We did an interface to a system running on 486 boxes, using 19.2Kbaud
modems. Those systems are still running today (and it's usually their
end running Gate$ware that has the problem) - Obligatory Windows
Shot


Changes to operational systems are co-ordinated very carefully as
there's much more at stake than just a software/hardware upgrade.
Requirements trace well beyond the nearest neighbor sometimes you
don't just do it because you can or it because it's cheap or because
it's cool or because someone proved it could work in a simulated
environment.

NAS Modernization is coming. But it won't come all at once. Much to
big a web (bad word choice) was woven over the decades to even
contemplate doing it any other way.


Were such messages transmitted by Morse code or something in the past, or is
someone still transmitting them that way (or over some other extremely slow
channel) today?

Yes, Morse code before WW-II. Afterwards, Teletype starting at 75
words per minute.

Interestingly enough, here's some GNSS datapoints:

GPS - 50 bps
WAAS - 250 bps



http://en.wikipedia.org/wiki/AFTN

http://users.bigpond.net.au/ctdavies...ed%20Telecommu...

http://www.sdxf.org/alfa/dxinfo/hfrtty.pdf

Good 'ole AFTN. Widely in use today domestically and esp.
internationally (many over PSNs - X.25 running over 64Kbit links)

Several sponsors (DFS, Airservices Australia, NavCanada, DECEA) all
require AFTN support.

Any you know what? It still works just fine.

What's typically done is to take advantage of encapsulation, to take
advantage of better Transport layers, while still maintaining
compatibility with existing systems.

Kev

Regards,
Jon