Motorola MSF 5000 Instruction Manual page 96

MSF
5000
Instruction Manual
Chapter
1
Description
68P81092E02 3/19/94
Uniboard
FROM PA
KEY
>
TOIPA
FROM OPTIONAL
CIRCULATOR VIA
INTERCONNECT
*
FROM
DRIVERAMP
TO SSCB
FROM
FINAL/DRIVER AMP
HEAT SINK VIA
INTERCONNECT
AMP
NAL
FORWARD POWER
.
TO IPA
TO
TX
METERING
JACK
*
Only used-in High Power Stations e
MSFX019.
022494KOM
SSCB
DR
VER
FORWARD
OVERDRIVE
POWER
SET
ae
POWER
CUTBACK
CIRCUITS
R453
PA
ROWER
PWR CUTBACK
CUTBACK
ADJUST
POWER
CUTBACK
DETECTOR
MEE
LN RS
Bea
POWER
SET
R426
FINAL
REFLECTED POWER
FROM
FINAL
FORWARD
CONTROL
VOLTAGE
"acs
Figure
1-28
Power Control Circultry
Block
Diagram
RF
Power Leveling Circuit
During
normal operation, the station
output power is controlled
by
the
RF
power
leveling
circuit.
This circuit maintains station output power constant over
variations in supply voltage and
PA
temperature.
This circuit disables the
IPA
during standby
(receive) mode and prevents uncontrolled station output
if
the
power control loop should fail.
When a
PTT
signal is generated,
the
IPA
is enabled for transmission
via
an
RF
switch. The IPA output is low-pass filtered
to
drive
the
PA. The
PA
contains
a
forward power sensor to detect
PA
output. The
PA
output supplies
a
DC
voltage
proportional
to
the power output for the control circuit.
The power control circuit varies its control output
until
the forward power sense
voltage is equal to the
power
set
voltage.
During
normal operation, the
PA
On
and
PA Full LEDs
on the
SSCB
are
illuminated.
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