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The test box remains in receive mode until a DSC call is received. A press on the EXIT button
can interrupt the mode, provided that the test box has not started to receive a call, in which case
you have to wait for a few seconds.
MMSI number, received data, and the MARK/SPACE frequencies are presented in the display
and stored in memory, provided that the checksum is OK.
Test results are displayed line by line. Press ↓ or ↑ to toggle between the lines.
If the MARK/SPACE frequencies do not appear on the LCD display, the signal is most likely
outside the limits 1770-1800 Hz / 1600-1630 Hz, or the signal was unstable during the header
or that the header was too short (less than 11 bit).
If data are shown as 255, it's because they were received in error.
Example of Printout from the Memory:
MF/HF # 1 Time/date: 08:25:18 / 21-11-2011
DSC DATA: 2187.5 kHz RX MMSI: 2195576240 Format 120 Cat.: 108
TX MMSI: 9999999990 Telecommand: 118 126 126 126 126 126 126 126
EOS: 117 ECC: 86 Status: OK
Mark: 2187414 Hz Space: 2187584 Hz
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/HF 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 must be within 1615 +/-15
Hz and 1785 +/-15 Hz respectively to be accepted.
Send DSC
In the Send DSC mode, the test box will transmit a DSC call for you to check on the DSC
receiver accordingly.
It is a requirement that the MMSI number registered in the test box is identical with the MMSI of
the radio to be tested. Please check and change number, if required, using the Edit ship's MMSI
menu. See Page 12.
With selective calls, connect the relevant antenna supplied with the test box to RF OUT and use
the setup below. The test box antenna should be able to "see" the transmitter's antenna.
DSC RECEIVER
ANT.
20
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