[ScanIndiana] Re: ACARS

[David L Norris]

On Mon, 2004-10-11 at 21:51 -0500, Eric Sluder wrote:
> Have any of you been successful in monitoring ACARS traffic on the air band?

Sure, it is rather trivial to do.  You simply need a radio capable of
demodulating 6KHz wide AM signals on the aircraft bands (131.55 MHz
mainly).  Connecting to the speaker or record jack works with some
radios but not others.  You may need to tap the radio's audio before the
internal squelch and filtering circuits.  You may not be able to just
connect to the speaker or record jacks.  Most radios have audio filters
which filter out the data tones.  

There are many programs that will decode ACARS and most use a sound
card.  Since it is AM signal strength and noise are major factors.  Any
noise whatsoever on the signal makes it impossible to decode.  The data
bursts are very susceptible to interference from, sometimes inaudible,
pops and clicks.

I was using acarsd on Linux a few years ago.  It supports sound card
decoding and on Windows it can communicate with the radios via Airmaster
or Skyspy.  You leave acarsd running 24/7 on one machine (Linux or
Windows) and it logs all traffic on the ACARS channel.  Then you can
access the logs using one of various graphical front-end programs.  You
can then plot the aircraft courses on world maps, generate graphs of the
various types of aircraft passing over your area, cross-reference tail
numbers with aircraft registration info, and so on right within the
program.  And for many commercial (and some private) aircraft you can
instantly bring up (or upload) a photo of the aircraft; not just a photo
of that type of aircraft but a photo of that very aircraft itself.
(Although taking photos of aircraft these days would probably get you
shot on sight. ;-)

There are screenshots of the Java graphical interface for acarsd:
  http://www.acarsd.org/screenshotc.html

-- 
 David Norris
  http://www.webaugur.com/dave/
  ICQ - 412039