4.10 Chassis
The high voltage and low voltage power supplies, as well as the driver switch logic board are
mounted on the bottom side of the chassis.
4.11 RF Output Filter & Reflectometer
The RF low-pass filter/reflectometer is located in the right-hand compartment on the top of the
chassis. See Illustration 6–13 and accompanying schematic for more information.
A ninth-order, elliptic, low-pass filter attenuates harmonics generated in the power amplifier.
The capacitors for the filter are circuit board pads.
The reflectometer uses printed circuit board traces for micro-strip transmission lines. Trans-
mission line segments (with an impedance of about 82 ohms) on either side of a 50–ohm con-
ductor provide sample voltages representative of the square root of forward and reverse
power.
DC voltages, representative of forward and reflected power, go through a bulkhead filter board
to the motherboard, then to the metering board, where they are processed for power control
and metering and for SWR metering and protection.
Driver Switch
Logic Board
High Voltage
Supply
Low Voltage
Supply
Illustration 4–8 Chassis Bottom View
Principles of Operation 4-15
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