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FIGURE 4.  FUNCTIONAL BLOCK DIAGRAM
RECEIVER

TM-55-1930-209-14P-12 Water Purification Barges (NSN 1930-01-234-2165) Lighting System Manual
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TM 55-1930-209-14&P-12 3. Unlock Detection In  the  event  that  the  lock  state  is  not  obtained,  the  logic  circuit  automatically  inhibits  the  transmitter  to  prevent illegal transmissions. TRANSMITTER The transmitter is designed for operation in the VHF Marine frequency range of 156 - 158 MHz. 1. Microphone Amplifier The audio signal originated at the microphone is applied to a microphone amplifier circuit consisting of a high pass filter, a microphone amplifier, a 6 dB pre-emphasis network, instantaneous deviation control (I.D.C.), and a low pass filter. The amplified audio signal is fed to the PLL frequency synthesizer to obtain an FM modulated RF signal. 2. Small Signal Stage The modulated RF carrier output from the PLL frequency synthesizer is applied to the RF amplifier stages (Q501 and Q502). 3. Power Stage The RF signal from the small signal stage is fed to a power amplifier stage consisting of a pre-driver (Q503), driver (Q504), and final transistor (Q505). 4. Output Filter/Matching Network The transmit signal, having been amplified by the power stage, is fed through a four-stage filter network to remove unwanted signals and to in- sure proper matching to the antenna.  This section also includes a solid- state antenna switching circuit to supply the signals received at the antenna to the receiver circuit, and an RF power sensor to send information to the power control circuit. 5. Power Control Circuit The DC signal which is sent from the sensor causes a voltage regulator to respond, levelling the transmitter output power and, if high VSWR is present in the antenna line, automatically reducing the power to a safe operating level.  The output power in high and low modes are individually adjustable. RECEIVER The receiver is a double conversion superheterodyne designed for operation in the VHF Marine frequency range of 156-163 MHz. 1. RF Stage The RF signal is picked up at the antenna and fed into a two-stage bandpass 10







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