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FAX systems are not intended as replacements
for other standard communications methods.
They are a useful supplemental system for rapid
communications.
Fleet Broadcasts
Radio traffic is sent to the fleet by two
methods: broadcast and receipt. The first is a “do
not answer” method; the second, as its name
implies, requires a receipt from addressees for
each message. The broadcast method allows the
fleet to preserve radio silence, which is a
great advantage from the standpoint of security.
Civilian and naval broadcasts have some
similarity. Commercial stations in the broadcast
band transmit programs to radio receivers in the
homes in their communities. Likewise, Navy com-
munications stations broadcast messages to fleet
units in their particular geographic areas. The
term broadcast, in fact, originated in naval
communications.
The resemblance between Navy commercial
stations ceases here, however. Information
broadcast by naval communications stations is
contained in chronologically numbered messages
assigned to the ships. Fleet units copy the
messages and check the numbers to ensure they
have a complete file of all messages they should
have received.
Automated systems now key fleet broadcasts.
Messages are broadcast in their order of
precedence. If the automated system receives a
higher-precedence message while transmitting a
lower-precedence message, it may interrupt the
latter to transmit the higher-precedence message.
All ships copy all messages addressed to them
that appear on the broadcast schedule they are
guarding.
Fleet broadcasts use satellites as their primary
transmission media, High-frequency (hf) radio
transmission provides broadcast services to ships
that are unable to copy the satellite systems.
Satellite Communications
A satellite communications (SATCOM)
system is one that uses earth-orbiting vehicles or
satellites to relay radio transmissions between
earth terminals.
A typical operational link involves a satellite
and two earth terminals. One station transmits to
the satellite on a frequency called the up-link
frequency. The satellite amplifies the signal,
translates it to the down-link frequency, and then
transmits it back to earth where the signal is
picked up by the receiving terminal.
The Commander, Naval Telecommunications
Command (COMNAVTELCOM), is designated
the communications manager for Navy-assigned
satellite systems. The responsibilities of the
communications manager include operating the
earth terminals and publishing Satellite Com-
munications Operating Procedures (NTP-2).
Commander, Naval Space Command (COM-
NAVSPACECOM), is the operational manager
for Navy satellites. The operational manager plans
the location of spacecraft and fixed earth
terminals and allocates satellite capacity, power,
bandwidth, and operating frequencies.
The Navy uses two primary SATCOM
systems:
• Long-haul (long-distance) communications
takes place via the defense satellite communica-
tions system (DSCS), which is managed by the
Defense Communications Agency (DCA). This
high-capacity global system uses satellites equally
spaced around the world operating on superhigh
frequencies (shf). Ships and stations located
anywhere on the earth from 70 degrees north
latitude to 70 degrees south latitude have access
to one of these satellites.
• The fleet satellite communications
(FLTSATCOM) system operates at ultrahigh fre-
quency (uhf), making possible the use of relatively
low-cost terminals and simple antennas. Leased
satellites (LEASAT) are part of this system.
• FLTSATCOM provides the primary
means of Navy tactical satellite ship-shore-ship
communications over the officer in tactical com-
mand information exchange subsystem (OTCIXS)
and the tactical data exchange subsystem
(TADIXS). The common user digital information
exchange system (CUDIXS) and the naval
modular automated communications system
(NAVMACS) combine to form a general-service
message traffic network.
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