connected to radio set control, C-1138. The radio setcontrol output is fed to transmitter transferswitchboard, SB-988/SRT. The switchboard performsthe same function as it does in the lf and hf systems.The output of the switchboard is connected to thetransmit side of the transmitter/receiver (transceiver),AN/VRC-46 or AN/VRC-80. The transceiver convertsthe input signal to an rf signal for transmission and therf is radiated into the atmosphere by the antenna.in sight of each other, though the distance traveledby the signal is much greater than for surfacecommunications.The uhf system uses a transceiver. However, wewill still describe the transmit and receive functionsseparately. Although this description pertains to voicecommunications, uhf equipment can process tty data inthe same way that the hf system does.Vhf ReceiveUhf TransmitAgain, look at figure 2-7. The incoming signal ispicked up by the antenna. This signal is fed to thereceive side of the transceiver. The transceiver outputis fed to the receiver transfer switchboard. Theswitchboard output is connected to either radio setcontrol or to a speaker amplifier, AM-3729, or both,depending on the user’s preference. The output of theradio set control is fed to the handset and the speakeramplifier output is routed to the speaker.ULTRAHIGH-FREQUENCYCOMMUNICATIONSThe ultrahigh-frequency (uhf) band is used forline-of-sight (short range) command and controlcommunications. As we stated earlier, line-of-sightmeans 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 remainA basic block diagram of a uhf transmit systemis shown in figure 2-8. On the transmit side of thenonsecure voice system, the operator at a remotelocation talks into the handset. The handset isconnected to a C-1138 radio set control. The radio setcontrol is connected to an SB-988/SRT transmittertransfer switchboard, which is connected to thetransmitter.On the transmit side of the secure voice system, theoperator talks into the secure voice remote phone unit(RPU). The RPU is connected to the secure voicematrix, which is the tie point for the connection ofmultiple remote phone units. The matrix output is fedto the secure voice equipment that encrypts theinformation. This encrypted information is then fed toan SB-988/SRT transmitter transfer switchboard.The transmitter switchboard performs the samefunction we described for previous systems. Theswitchboard output is connected to the transmit side ofthe AN/SRC-20/21 or AN/WSC-3, which is connectedFigure 2-8.—Uhf transmit.2-8
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