When a ship requests simplex operation on duplex
circuits, the shore station may be required to shift
transmitters prior to acknowledging call-up. If no reply
is received within 45 seconds, the ship should repeat the
call-up procedures. If a third attempt is required, the
ship should check equipment to ensure proper
operation.
Semiduplex
Semiduplex communications circuits, used
primarily on task force/task group/ORESTES, are a
combination of the simplex and duplex modes. All
stations except the net control station (NECOS)
transmit and receive on the same frequency. The
NECOS transmits and is received on a second
frequency. The NECOS may transmit continuously,
whereas all other stations must transmit in accordance
with simplex procedures.
UHF/HF RELAY
The UHF/HF relay method permits long-range,
uninterrupted communications during periods of
hazardous electromagnetic radiation (HERO). Figure
1-13 shows a block diagram of a UHF/HF voice relay
circuit.
Modern radio and radar transmitting equipments
produce high-intensity RF fields. It is possible for RF
energy to enter an ordnance item through a hole or crack
in its skin or to be conducted into it by firing leads,
wires, and the like. Here is an example of HERO. An
aircraft carrier is arming aircraft on board. During
arming operations, all HF transmitters must be secured
to prevent possible detonation of the ordnance. To
maintain its ship-shore communications, the carrier
transmits to a relay ship via a UHF circuit. The relaying
ship then retransmits the signal on a HF circuit to a
terminated NAVCOMTELSTA. On-line
Figure 1-13.—UHF/HF voice relay circuit.
1-12
