ULTRAHIGH-FREQUENCY COMMUNICATIONS

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