connected to radio set control, C-1138. The radio set
control output is fed to transmitter transfer
switchboard, SB-988/SRT. The switchboard performs
the same function as it does in the lf and hf systems.
The output of the switchboard is connected to the
transmit side of the transmitter/receiver (transceiver),
AN/VRC-46 or AN/VRC-80. The transceiver converts
the input signal to an rf signal for transmission and the
rf is radiated into the atmosphere by the antenna.
in sight of each other, though the distance traveled
by the signal is much greater than for surface
communications.
The uhf system uses a transceiver. However, we
will still describe the transmit and receive functions
separately. Although this description pertains to voice
communications, uhf equipment can process tty data in
the same way that the hf system does.
Vhf Receive
Uhf Transmit
Again, look at figure 2-7. The incoming signal is
picked up by the antenna. This signal is fed to the
receive side of the transceiver. The transceiver output
is fed to the receiver transfer switchboard. The
switchboard output is connected to either radio set
control or to a speaker amplifier, AM-3729, or both,
depending on the user’s preference. The output of the
radio set control is fed to the handset and the speaker
amplifier output is routed to the speaker.
ULTRAHIGH-FREQUENCY
COMMUNICATIONS
The ultrahigh-frequency (uhf) band is used for
line-of-sight (short range) command and control
communications. As we stated earlier, line-of-sight
means that both antennas are aimed at one another,
with no obstruction in between.
This band is also used for satellite com-
munications. Satellite communications are line-of-
sight communications because the antennas remain
A basic block diagram of a uhf transmit system
is shown in figure 2-8. On the transmit side of the
nonsecure voice system, the operator at a remote
location talks into the handset. The handset is
connected to a C-1138 radio set control. The radio set
control is connected to an SB-988/SRT transmitter
transfer switchboard, which is connected to the
transmitter.
On the transmit side of the secure voice system, the
operator talks into the secure voice remote phone unit
(RPU). The RPU is connected to the secure voice
matrix, which is the tie point for the connection of
multiple remote phone units. The matrix output is fed
to the secure voice equipment that encrypts the
information. This encrypted information is then fed to
an SB-988/SRT transmitter transfer switchboard.
The transmitter switchboard performs the same
function we described for previous systems. The
switchboard output is connected to the transmit side of
the AN/SRC-20/21 or AN/WSC-3, which is connected
Figure 2-8.—Uhf transmit.
2-8
