FAX 5/10/20/30/40KW
October 28, 2013
4
‐
9
888
‐
2720
‐
001
WARNING:
Disconnect
primary
power
prior
to
servicing.
Copyright
©2013,
Harris
Broadcast
To
make
the
module
safe
to
hot
plug
it
the
traces
for
the
RF
output,
RF
input
and
+VDD
are
a
different
length,
See
Figure
4
‐
9.
The
RF
output
traces
are
longest
so
when
inserting
a
module
the
load
is
the
first
to
be
connected.
When
removing
a
module
the
load
will
be
the
last
to
be
disconnected.
Next
in
length
is
the
+VDD
and
finally
the
last
to
be
connected
inserting
and
the
first
to
be
disconnected
removing
a
module
is
the
RF
input
drive.
Figure 4-9 PA Module Edge Connector
The
+VDD
PA
voltage
has
a
range
from
+44
VDC
to
+52
VDC.
The
actual
voltage
varies
depending
on
which
mode
the
transmitter
is
in:
FM
only,
FM
+
HD,
or
HD
only
mode.
The
reason
to
have
different
voltages
for
different
modes
is
to
maximize
transmitter
PA
efficiency
and
spectrum
performance.
The
gate
bias
circuit
performs
3
functions:
PA
ON/OFF,
Class
C
Bias
for
FM
Mode
of
operation,
and
Class
AB
Bias
for
HD
Modes.
A
control
voltage
of
‐
5V
at
J2
‐
4
turns
Q5
off
which
allows
the
RF
Amplifier
to
operate.
The
Bias
Mode
voltage
alters
the
PA
bias
voltage
to
cause
the
PA
amplifier
to
operate
at
Class
AB
or
Class
C.
The
control
voltages
come
from
the
module
Control
board.
Thermistors
RT1
and
RT2
are
used
to
stabilize
the
bias
as
the
temperature
of
the
module
varies.
Pots
R102
and
R103
are
set
at
the
factory
to
precisely
set
the
Class
AB
bias.
Pots
R101
and
R104
are
adjusted
for
Class
C
operation.
These
pots
should
not
be
adjusted.
Thermistor
RT3
monitors
the
heatsink
temperature.
If
the
heatsink
temperature
gets
too
high
(90
°
‐
100
°
C),
the
Module
Control
board
will
shut
off
the
full
PA
Module.
4.1.8
Power Supply System Description
The
Power
Supply
Interface
Board
performs
several
functions
as
follows:
•
Interfaces
power
supplies
DC
output
with
the
PA
modules
•
Busses
dc
from
supplies
for
IPA
and
fans
•
Monitors
AC
line
for
under
voltage
•
Monitors
airflow
and
exhaust
air
temperature
•
Provides
distribution
of
the
+5
VDC
to
the
rest
of
the
system
Figure 4-10 Power Supply Interface Board
RF Output
RF Input
+VDD
Summary of Contents for Flexiva FAX 10KW
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