1 The VHF EPIRB DSC distress alerting signal should be
transmitted on the frequency of 156.525 MHz using G2B class of emission.
2 The frequency tolerance should not exceed
10 parts per million.
3 The necessary
bandwidth should be less than 16 kHz.
4
The output power should be at least 100 mW.
5 The emission should be vertically polarized at the source.
6 MODULATION
6.1 Frequency modulation with a pre-emphasis characteristic
of 6 dB/octave (phase modulation) with the modulating subcarrier, should be used.
6.2 A subcarrier of 1,700 Hz with
frequency shift between 1,300 Hz and 2,100 Hz should be used.
6.3 The frequency tolerance of 1,300 Hz and 2,100 Hz tones
should be within ± 10 Hz .
6.4 The
modulation rate should be 1,200 bauds.
6.5 The index of modulation should be 2.0 ± 10%.
7 DSC MESSAGE FORMAT AND TRANSMISSION SEQUENCE
7.1 The technical characteristics for the
DSC message should be in accordance with the sequence for the "distress call"
specified in CCIR Recommendation 493.
7.2
The "nature of distress" indication should be "EPIRB emission".
7.3 The "distress co-ordinates" and "time" information
need not be included. In this case the digit 9 repeated 10 times and the digit 8
repeated 4 times should be included as specified in CCIR Recommendation 493.
7.4 The "type of subsequent communication"
indication should be "no information" (symbol # 126) which indicates that no
subsequent communications will follow.
7.5 The alerting signals should be transmitted in bursts. The (N + 1)
burst of transmission which consists of five successive DSC sequences should be made
with an interval of Tn after the (N)th burst as given in figure 1.
Where: Tn = (230 + 10N) seconds ± 5% and N = 1, 2, 3, ...