"Al Klein" wrote in message
...
On Sun, 9 Oct 2005 09:42:00 +0100, "Andy100" said in
rec.radio.scanner:

Anyway, just like we can now decode pager messages, ACARS etc, i thought
maybe somewhere this software existed. I don't mean free software which
will
place the aircraft on a radar screen, but just simple software which
would
at least decode what flight number the aircraft was at least ?. I can
pick
the signals up no bother, would be interesting to decode them !!


You could just monitor the output of the detector with an oscilloscope.

Basically, they aren't tone bursts. There are two types of signal
transmitted depending on mode. One is a pulsed carrier containing binary
coded pulses 0.45uS wide. The other is a phase modulated carrier.

Most of the information transmitted is just numbers and if there are VFR
aircraft around, a lot of those numbers will simply decode as 1200, with an
altitude.

Brad