NAVTEX in operation since August 1993; 


NAVigational TEXt (NAVTEX) is a Narrow Band Direct Printing (NBDP).

Transmission in --> SITOR mode B            (simplex telegraph over radio)

Code for tx is  --> CCIR 476 character set  ITA2 extended by 2 bits to 7 bits

Speed           --> 100 Baudot
                    100 bits/second, 1 bit in 10 ms
                    1 character in 70 ms

Method          --> Frequency Shift Keying, FSK 170 +/-Hz shift

Foreward error  --> FEC, each character sent twice
correction

Timeslot            10 minutes = 600 seconds

Maximum         --> 600 * 100 = 60000 bits
characters per      60000 / 7 = 8571 characters brutto
timeslot            8571  / 2 = 4285 characters netto, because of FEC
                    (approximate values)

Text capacity   --> 122 lines text by 35 characters per line
                    2 pages of 61 lines per page, by 35 characters per line
                    Example of a text line :
                    '0        1         2         3     '
                    '12345678901234567890123456789012345'