PSK: VDL-2 (VHF) - AirSystem, PSK-8, Br - 10500

VDL-2 (VHF)

AirSystem, PSK-8, Br - 10500

Author: SergUA6 

Band Width ~17000 Hz

Baud Rate 10500 Hz

n-Ary (PSK/MPSK) PSK-8

RX mode source I/Q record

                                                                

          Here is example of VDL-2. Sent by foregin collegues.

Sonograms:

pic.1 General view

pic.2 Manipulation speed

Pictures

pic.3 Phase constellation

VDL-2 - It is rather new and the perspective view of aviation telecommunication (ATN). It is very actively introduced in practice. It is provided step-by-step change/move from the previous generation of similar system ACARS, to the new VDL-2, VDL-3. As well as in ACARS, data exchange between aircrafts and the earth occurs by extremely short packages. In average, lenght of the package is about 20-40 мс, but it can be both shorter and longer packages. In comparison with ACARS, the throughput of channel ATN in VDL-2 is essentialy increased from 2400 bps (ACARS) to ~31500 bps.


As a whole, at appropriate quality, the signal is confidently enough analyzed and identified, there are no obvious features detected.

The example of the analyzed signal

The ACARS VHF signal
AirSystem

the signal is here http://signals.radioscanner.ru/base/files/signal24/f1.wav

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.