FHMUX Performance Data

TM 11-5820-890-10-8

FHMUX Performance Data

3.3c.

Vehicular Configuration

Figure 3-5 shows a typical vehicular configuration using one multiplexer and two VRC-92A radios. The

introduction of the multiplexer into the radio system is "transparent", that is it does not affect the way the radios

are operated. The number of vehicular antennas needed is reduced from four to one. Instead of each radio

going directly to its own antenna, the antenna connections of the four radios are routed to the multiplexer and

the multiplexer then connects to a single common antenna. To provide frequency hopping information to the

multiplexer, the SNAP control signals provided by the VAA must be connected to the multiplexer, one SNAP

cable per VAA. Vehicular DC power (22 to 32 Vdc) must also be supplied to the multiplexer through J2 on the

Power Amplifier Mount (MT-6353/VRC) or through J2 on the Mounting Base (MT-6576/VRC).

The only two operator controls on the multiplexer are the POWER switch and the RADIO PRIORITY switch. The

POWER switch must be placed in the ON position to use the FXMUX (the POWER switch can be turned ON and

left ON if the DC power is controlled remotely by CB1 on the VAA).

Figure 3-3. POWER Switch

The RADIO PRIORITY switch position is set based on the desired operating scenario. In the EQUAL position, all

four radios connected to the multiplexer will have equal communications priority. In the 1A, 1B, 2A and 2B

positions, the selected radio will have a slightly higher priority than the other radios whenever there is frequency

conflict (a frequency conflict is when two or more hopping radios want to communicate on the same frequency

at the same instant). In the RXMT(1A+1B) position, radios 1A and 1B (operating in the retransmit mode) have

higher priority than radios 2A and 2B. Normally the switch will be set in the EQUAL position, but if desired, higher

priority can be given to a critical communications link

Figure 3-4. RADIO PRIORITY Switch

The TEST position is used only for Off -Line BIT and the switch should not be placed in this position except as

directed in the -20 and -30 maintenance manuals.

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