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10-4
LPF Unit (PC1817)
In the L.P.F. (output low pass filter) circuit, there are seven band filters that are
selected by the manual band switch. Each L.P.F. is used to reject harmonics so that
the amplifier meets international telecommunication equipment standards,
including FCC rule.
10-5
Control Unit (PC1818)
This is the heart of the control signal processing for the HL-550FX. It judges the
operating condition of the amplifier, as well as issuing the commands to the
peripheral circuits. Various analog signals are processed such as RF drive from the
transceiver, RF power signals at various points, DC power supply information, etc.
There are ope-amps, various three terminal voltage regulators, GAL logic device
etc. Warning signals are processed by the logic IC for Over Heat, Over Voltage, Pr,
Band Miss-set etc. Ope-amps produce the necessary DC signals to drive the Pf, Pr
meters. Also there is a control circuit that issues the drive shut down command in
case of the over drive, band miss-set and high antenna SWR conditions.
10-6
Power Supply
The main DC power supply feeds the 44V DC power to the final PA stage. It is a
state of art, switching power supply with high efficiency.
Sub AC power supply, feeding ±15V is also installed to consist a high quality
power circuit, along with the LPF circuit.
16
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