Product Info

PTR for VHF-4000 and VDL-2000 Data Radios

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Appendix C - VDL Mode 2 Operation

The BFR test message is a VDL Mode 2 message containing 249 application bytes. The message will also

contain 6 Reed Solomon check bytes for a total of 255 bytes. The normal VDL preamble containing the

following segments must also be contained in the message:

a) 12 bits (4 symbols) for transmitter power ramp up;

b) 48 bits (16 symbols) for synchronization

c) 3 bits as the reserved symbol

d) 17 bits transmission length

e) 5 bits header FEC.

Refer to DO-224A, “Signal-in-Space Minimum Aviation System Performance Standards

(MASPS) for Advanced VHF Digital Data Communications Including Compatibility with

Digital Voice Techniques”, September 13, 2000, for specific details on the composition of

VDL Mode 2 message and waveform.

A suitable test message is shown in hex format as follows :

The message starts with 000 hex which is 12 bits (4 symbols) of constant signal which is

the ramp up for VDL Mode 2.