comdtinst m2400.1f - US Coast Guard Response Boat-Medium

6.B.4. Operational Areas. Operational areas have been designated to
determine equipment carriage requirements for vessels and appropriate
communication systems to employ for distress alerting and
communications (see paragraph L below).
(a) Area A1 - within range of shore based VHF stations
(b) Area A2 - within range of shore based MF stations (excluding A1
areas)
(c) Area A3 - within the coverage area of geostationary satellites
for maritime communications (excluding A1 and A2 areas)
(d) Area A4 - outside the coverage area of geostationary satellites
5. INMARSAT. Satellite communications may be used in both the
ship-to-ship and shore-to-ship directions. The INMARSAT
system, which uses geostationary satellites and operates in
the 1.5 to 1.6 GHz bands, will provide a means of alerting
from ships and for two way communications using radiotelephone
and NBDP. Polar orbiting SARSAT satellites will provide a
means of distress alerting and position location of EPIRBs in
the 406 - 406.1 MHz band. Basic ship-board equipment will
consist of a ship earth station, approved by INMARSAT
(Standard A or C terminal), and satellite EPIRBs.
6. HF. HF will provide long range communications in the
ship-to-shore and shore-to-ship directions. In areas covered
by INMARSAT, HF can be used as an alternative to satellite
communications. Outside these areas it will provide the only
communications capability. Frequencies have been designated
in the 4,6,8,12 and 16 MHz bands to provide for distress
alerts, safety calls and for passing distress and safety
traffic. HF distress and safety traffic will be transmitted
by radiotelephony and/or NBDP.
7. DSC. DSC will be used for distress alerting and safety calling.
Choice of the appropriate band to use will be determined by the
geographic area to be covered and propagation conditions. Current
planning is for ships using the HF option to maintain a watch on the 8
MHz alerting frequency and one other HF frequency appropriate for the
Area in which the ship is operating. The Coast Guard will use DSC
primarily as a means of initiating a radiotelephone (voice) call.
8. MF. MF will provide medium range communications in the ship-to-shore,
ship-to-ship and shore-to-ship directions. Distress alerts and safety
calls by DSC will be on 2187.5 kHz. Disresss and safety traffic by
radiotelephony, including SAR coordinating functions and on scene
communications will be on 2182 kHz. Distress and safety traffic by
NBDP will be on 2174.5. Navigational and meteorological warnings
using the NAVTEX system will be on 518 kHz. A complement of HF NBDP
Channels will be available on 1 July 1991 to provide high sea maritime
safety information. The frequency 490 kHz will be available at a
later date to supplement NAVTEX in the shore-to-ship direction.
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