понедельник, 4 мая 2009 г.

The example of the analyzed signal

The ACARS VHF signal

the signal is here

Author - SergUA6

Band Width - 2400-2700 Hz

Low Range - 300-400 Hz

Baud Rate - 2400 Hz

Count of Carriers – There are two practically not distinguishable frequencies of manipulation,
with strongly fixed values of 1200 and 2400 hertz, hard fixing is provided by a transmission mode with AM(amplitude modulator).

Step between carriers - 1200 Hz

RX mode – AM

Sonogram pic.1

Diagram pic.2

Diagram pic.3
ACARS VHF - it is one more system that is used in aircraft, in difference from HFDL, it is used only on VHW and only in AM mode, range of operation is limited by a working range of used frequencies and does not exceed 400-500km. Modulation of radiation is АМ, the signal represents GFSK manipulation with carriers 1200 and 2400 hertz and with speed of manipulation of 2400 hertz. There shouldn’t be difficulties with identification of this signal. At first there are no any signals in AM mode in aviation range with such characteristics, secondly the signal has features, which are very well visible after demodulation(check graphics), thirdly the signal has standard frequencies, which are must be known, because, by virtue of the very short time of transmission, to meet these signals accidentally is very hard.

This signal is analyzed and ready for decoding.