VERY-HIGH-FREQUENCY SYSTEMS

The very-high-frequency (VHF) band (30-300 MHz) is used for aeronautical radio navigation and communications, radar, amateur radio, and mobile communications (such as for boat crews and landing parties). Figure 1-4 shows a basic block diagram of a

Figure 1-4.-Very-high-frequency transmit and receive system.

VHF transmit and receive system using a transceiver. Although a transceiver is used in this system, the transmit and receive systems are described separately. Refer to figure 1-4 as we follow the signal path on the transmit side of the system.

On the transmit side of the system, the operator, at a remote location:

1. Talks into the handset.

2. The handset is connected to the C-1138 Radio Set Control.

_3. The output of the radio set control is sent to the transmitter transfer switchboard.

4. The output of the switchboard is sent to the transmit side of the transceiver.

5. The transceiver converts the input signal to an RF signal for radiation by the antenna.

Continue to refer to figure 1-4 as we follow the path of the incoming signal.

1. The incoming signal in figure 1-4 is received by the antenna.

2. This signal is sent to the receive side of the transceiver.

3. The output of the transceiver is sent to the receiver transfer switchboard.

4. From the receiver transfer switchboard, the output is sent to either the C-1138 Radio Set Control or to a speaker amplifier, or both, depending on the preference of the user.

5. The output of the radio set control is sent to a handset.

6. A speaker receives the output of the speaker amplifier.