OPERATIONAL OR TACTICAL
CIRCUITS
Most voice circuits used at sea are operational or
tactical nets; some circuits, however, are often used to
pass administrative traffic. These circuits are
subcategorized into two distinct types: short and long
range.
Short-range operational communications normally
use the UHF frequency spectrum (225 to 400 MHz) and
low-power, line-of-sight equipment. Because of these
frequency and equipment characteristics, the maximum
effective range is usually 20 to 25 miles. This limited
UHF range offers no security, and transmissions are
always subject to enemy interception. However, since
these transmissions are limited somewhat to the local
geographic area, interception by an enemy would be
difficult. On the other hand, the range of UHF
communications may be extended through the proper
use of relay procedures.
More and more, our modern and high-speed ships
must report to OTCs from longer distances than the
older ships they replaced. Long-range frequencies in the
medium- and high-frequency spectrum (2 to 32 MHz)
are, therefore, used. From your study of module 4, you
will remember that the propagation characteristics of
these frequencies make them desirable for long-range
communications. To further increase the range
capabilities of long-range communications, we use
single-sideband (SSB) methods.
ADMINISTRATIVE CIRCUITS
Administrative circuits are normally used only in
port and may include both short- and long-range
communications. Voice circuits that are neither
operational nor tactical are included in the
administrative category. Seldom is there such a circuit
in at-sea communication plans.
Harbor common circuits and tug control nets are
two examples of administrative nets. Naturally, these
nets assume an operational function during situations
requiring emergency procedures, such as natural
disasters and civil uprisings. Circuit requirements vary
from port to port, as established by the senior officer
present afloat (SOPA). Both the UHF and MF/HF
circuits may be used for administrative nets.
TYPES OF NETS
There are two types of R/T nets: directed and free.
The type of net to be used is determined by the
operational situation. Regardless of the type of net used,
a Net Control Station (NECOS) is assigned to monitor
the circuit or circuits and enforce circuit discipline.
NECOS is the senior net member or designated
authority. The NECOS is responsible for implementing
operational procedures and enforcing discipline and
security on the net. Enforcement of circuit discipline,
however, is not the only reason for having a NECOS.
Sometimes there are so many stations sharing a
common circuit that a NECOS is necessary to facilitate
the handling and passing of R/T traffic.
Directed Net
On a directed net, stations must obtain permission
from the NECOS before communicating with other
stations on the net. The exception to this rule is when a
station has FLASH traffic to send. Also, transmissions
on the directed net may be accomplished with a
predetermined schedule.
Free Net
On the free net, member stations don’t need NECOS
permission to transmit. Net members must ensure that
the net is not in use before initiating a call-up. A free net,
however, does not relieve the NECOS of the
responsibility for enforcing operational procedures and
maintaining proper circuit discipline.
Both free and directed nets normally use collective
call signs. Figure 2-1 diagrams an R/T net that consists
of the following stations: USS Key, USS Mariano G.
Vallejo, USS James K. Polk, USS Kamehameha, and
USS Tecumseh. In this example, we will assume that the
NECOS is Key. Notice that the collective call sign for
the entire net is Poseidon.
Figure 2-1.—Radiotelephone net.
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