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Chapter
1
Description
MSF
5000
Instruction Manual
Intermediate Power Amplifier
TO POWER AMPS
OR
PERIPHERAL
FROM
-
TX
ENABLE
VOLTAGE
VOLTAGE
SERIES
PASS
At
RE
N
TX
ATTENUATOR
RF
omn
LOW
ROUT
SWITCH
AMP
PAS
FILTER
UNIBOARD
CONTROL
MEFS
CONTROL
96V
UNFILTERED
+9.6
V
REGULATOR
TO
UNIBOARD
MSFX027
022194JNM
Figure 1-33
Intermediate
Power Amplifier Block Diagram
Power Amplifier Circuit
During
station transmission, the
RF
signal generated
by
the
transmit synthesizer
is applied
to the
IPA. The
RF
signal is routed
to the
OMNI
amplifier when
the
power control circuit
enables an
RF
switch.
The
OMNI
amplifier is
a
two
stage class
C
amplifier. The first stage is powered
by
the
A+
from the Power Supply. The second stage is powered and controlled
via
the series pass circuit.
The
RF
signal is amplified between
0
to
8
Watts, dependent on the control loop
feedback voltage at the input of the series pass circuit. When this voltage is
varied,
the
IPA
output power and
the station
output power can
be
varied
to
any
desired level
within
its operating limits.
During
standby (receive) mode,
a
specified minimum
RF
signal is allowed
to
conduct
to the
station output.
This
is due
to the
continuous operation of
the
transmit synthesizer circuit. However, the
RF
switch is turned off during standby
mode, preventing transmission of any significant output power.
1-62
68P81092E02
3/19/94
FROM
Chapter
1
Description
MSF
50
Instruction Manual
Intermediate Power Amplifier
RE
N
ATTENUATOR
RF
omn
SSS
LOW
ROUT
TO POWER AMPS
SWITCH
AMP
PAS
OR PERIPHERAL
FILTER
BOX
FROM
UNIBOARD
TX
ENABLE
ROL
MEFS
CONTROL
VOLTAGE
VOLTAGE
SERIES
PAS
9.6V
.
UNFILTERED +9.6V
REGULATOR
TO
UNIBOARD
MSFX027
022194JNM
Figure
1-3
Intermediate
Power Amplifier Block Diagram
Power Amplifier Circuit
During
station transmission, the
RF
signal generated
by
the
transmit synthesizer
is applied
to the
IPA. The
RF
signal is routed
to the
OMNI
when
the
power control circuit
enables an
RF
switch
The
OMNI
amplifier is
a
two
stage class
C
amplifier. The first stage is powered
by
the
A+
from the Power Supply. The second stage is powered and controlled
via
the series pass
circuit
The
RF
signal is amplified between
0
to
8
Watts, dependent on the control loop
feedback voltage at the input of the series pass circuit. When this voltage is
varied,
the
IPA
output power and
the station
output power can
be
varied
to
any
desired level
within
its operating limits
During
standby (receive) mode,
a
specified minimum
RF
signal is allowed
to
conduct
to the
station output.
This
is due
to the
continuous operation of
the
transmit synthesizer circuit. However, the
RF
switch is turned off during standby
mode, preventing transmission of any significant output
power
1-62
68P81092E02
3/19/94
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