DESCRIPTION
2.0 DESCRIPTION
The UHF Power Amplifier Assembly is a wide band RF power amplifier operating over
the 380-400, 410-430, 403-425, 425-450, 450-470, 470-494, and 492-512 MHz range
without tuning. Its main function is to amplify the 10 mW FM signal from the
Transmitter Synthesizer to the rated RF output at the antenna port. The output of the
Power Amplifier Assembly is adjustable from rated power to 3dB lower at the PA output
J104.
The assembly consists of a printed wiring board (A1) and associated components,
including a power module and three RF power transistors, mounted to the heat sink
assembly. The printed wiring board (A1) contains both the power amplifier circuitry and
the power control circuitry.
Unfiltered supply voltage, A+, for the power amplifier circuits enters the assembly via
feedthrough capacitor, C1. Power cable W4 routes the A+ from C1 to J103 on the PWB.
Filtered A+ voltage for the power control circuit enters the assembly via control cable
W13, which connects to the PWB at J201.
The Power Control circuitry sets the output power level by adjusting the PA Power Set
level. It keeps the output power constant despite variations in input power, power
amplifier gain, or temperature through the use of a feedback control loop in the PA
assembly.
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LBI-38674L
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