User's Manual

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１4 Block Diagram and Explanation of Major Circuitry
14-A RF Amp
Driving RF signal transmitted from the
transceiver is lead to the ATT/ Limitter board via
T/R-Assy unit, where there is 3dB attenuator as
well as RF limiter. These circuitry properly
levels the magnitude of RF signal and also
instantly shuts down the input to protect the
amplifier.
There is a three port splitter located in this
board that sprits a driving signal equally into
three components, which are then fed to final
PA module.
PA module consists of three sets of wide band
class AB1 linear amp. using THP2933 FET’s in
the push-pull form. 500W is achieved per one
basic amp. board. Then the three outputs from
the PA module is sent to the combiner unit,
where three 500W components are combined to
become 1,500W.
Operating status of three PA’s are strictly
monitored in the combiner stage with regard to
heat balancing of respective amps.
Finally 1,500W of RF output is lead to LPF (low
pass filter) unit, where harmonics and spurious
signals are reduced to FCC rules. Filtered
output signal is sent to T/R ASSY unit again and
is lead to antenna terminal by way of antenna
relay.