FM 24-18: Tactical Single-Channel Radio Communications Techniques
(TD-1288( )/GRC AND TD-1289( )(V)/GRC)
D-1. Use and Application
Command and control of the combat, combat support, and combat service support unit is dependent on responsive communications. The communications system must be responsive, highly reliable, and be available to meet the requirements of the force. The transceiver multiplexer enables as many as five tactical combat VHF-FM radios to operate simultaneously at the same location with a single broadband antenna. The transceiver multiplexer equipment assists in the rapid employment of the tactical command post FM communications due to the decrease in the number of antennas required to be erected.
The transceiver multiplexer in no way impedes the normal function of the individual transceiver of the net configuration. The multiplexer is capable of passing any type traffic within the 30 to 88 MHz frequency range with no degradation of radio planning range.
The multiplexer is not affected by communications security and requires no physical security other than that required for the entire radio system.
Technically, the multiplexer reduces or eliminates interference between receivers and transmitters in the VHF systems. It also reduces or eliminates interference to and from other sensitive electronic equipment.
Tactically, the multiplexer decreases the installation/displacement time of the tactical command post due to the decreased command post area. There is no direct effect on the transceiver multiplexer by EW operations. The multiplexer is electromagnetic pulse protected by design.
The transceiver multiplexer--
- Contains filter modules which are interchangeable within the mounting base.
- Contains termination units for terminating unused channels that are interchangeable with filter modules. The termination units prevent impedance mismatch losses and/or spurious emissions from degrading the performance of operating channels.
- Contains visual tuning indicators for each individual filter module to provide tuning and monitoring each channel.
- Introduces no more than a 2-dB insertion loss into the communications circuit.
- Contains input and output characteristics compatible with the AN/VRC-12 series radio to include OE-254/GRC biconical antenna and any other broadband antenna (50 ohm impedance).
- Permits independent operation of transceivers separated in frequency by at least 5 percent (1.5 MHz at 30 MHz, 4.4 MHz at 88 MHz).
- Provides circuitry to allow for monitoring the forward and reflected power of each transceiver and for monitoring both high (0-60 watts) or low (0-6 watts) transmitter power in order to facilitate tuning when operating with low power radios.
The transceiver multiplexer consists of either a two- or five-port unit. (See fig D-1).
Figure D-1. Transceiver multiplexer.
D-4. Associated Equipment
Tactical net radio (AN/VRC-12, AN/PRC-77, and AN/PRC-70).
Antenna system OE-254/GRC (or any other broadband antenna under development in the 30-88 MHz range).
All necessary coaxial cables and cable adapters.
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