Hi Deepak007,
The very first sentence in the paper u've sent clears u'r doubt. AIRCRAFT SIGNALS ARE BROADCAST IN AM FORMAT.
Here is my explanation: Please remember that as per ITU regulations, FM broadcast band is from 88-108MHz.But, if u r given permission, u can transmit FM signals on any freq. other than the std. freq.range used for radio broadcast.
Having said that, the same logic also applies for transmission of AM signals.Eventhough AM broadcast band is from 540-1650KHz, u can stll transmit AM signals in other freq. othan than the std.broadcast band.
The modulation technique assigned to transmit Aircraft signals is AM.But these signals can be txd. in any freq.range - in this case it is 108 to 138MHz(as per ITU regulations),which is the aircraft band and NOT the standard AM broadcast band.
Hope u got my answer.
Regards
Bhanumurthy.