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Measurement of MARK/SPACE Frequencies
The SPACE and the MARK frequencies are measured during the initial part of the DSC call.
The measurements are done by means of a time measurement on an AF signal (1700 Hz +/- 85
Hz) derived from the MF/RF MARK/SPACE signal.
The time measurements for MARK and SPACE respectively are converted to frequency and the
calculated values are added to an offset frequency for the actual MF/HF frequency. By adding
the offset frequency to the measured/calculated frequencies the actual MF/HF MARK/SPACE
frequencies are obtained.
The AF signal used for calculation of the MARK/SPACE frequencies has to be within 1615 +/-15
Hz and 1785 +/-15 Hz respectively to be accepted.
Example of Printout from the Memory:
CONTROL MEASUREMENT ON MMSI NO: 2734742100 - HOUR:12 DATE:21-06-2006
2187.5KHZ FORMAT: 120 ADR:2734742100 CAT: 100
SELFID:2734742100 109 126 126 126 126 126 126 126 117 122
SPACE/MARK FRQ: 2,187,588HZ, 2,187,417HZ
Receive ATIS
In RECEIVE ATIS mode keying of an ATIS equipped VHF on CH 6 or CH 15 will enable the test
box to receive and display the station’s ID. The data will be stored in the test box memory
accordingly.
ANT.
VHF ATIS TRANSMITTER