Section-4 Theory
October 28, 2013
4
‐
12
Copyright
©2013,
Harris
Broadcast
WARNING:
Disconnect
primary
power
prior
to
servicing.
888
‐
2720
‐
001
The
transmitter
configuration
is
stored
in
memory
on
this
board.
This
configuration
contains
the
user
setup,
ie
dual
exciter,
frequency,exciter
type,
etc,
as
well
as
all
calibrations.
This
file
is
a
downloadable
file
that
can
be
stored
on
a
computer
and
uploaded
in
the
event
the
Control
and
Display
board
needs
to
be
replaced.
It
is
a
good
idea
to
store
this
when
the
transmitter
is
first
installed
and
any
time
a
change
to
setup
or
calibration
is
completed.
The
board
also
provides
the
power
control
reference
to
the
System
Interface
board
APC
hardware.
This
reference
is
3.5
VDC
and
remains
constant
under
normal
conditions.
If
the
raise
or
lower
power
button
is
pressed
this
voltage
changes,
lower
power
will
lower
the
reference
voltage.
See
APC
and
System
Interface
for
further
details.
4.1.11
System Interface Control Board Description
The
FAX
10kW
transmitter
contains
a
System
Interface
control
Module
that
mounts
directly
to
the
right
of
the
Power
Supply
Modules.
This
board
provides
several
functions
for
the
transmitter
system.
•
Operates
as
a
transmitter
interface
or
a
power
block
interface
(FAX20/30/40)
•
Hardware
control
in
lifesupport
mode
•
Exciter
interface
and
exciter
RF
switching
•
The
APC
hardware
is
located
on
board
•
OptoCouplers
for
Remote
control
via
Parallel
I/O
•
Forward
and
reflected
power
detection
and
metering
samples
•
Hardware
for
VSWR
protection
and
power
limit
functions
•
System
status
LED’s
•
Multiplexing
bus
for
meter
readings
The
exciter
interface
can
be
setup
to
accept
any
exciter,
Harris
Broadcast
or
another
manufacturer.
If
a
non
‐
Harris
Broadcast
exciter
is
used
the
dipswitch
settings
will
need
to
be
properly
set
and
a
custom
interface
cable
made.
If
dual
exciters
are
used
the
RF
switching
is
done
on
board.
To
achieve
automatic
switching
a
DC
voltage
proportional
to
RF
power
must
come
from
the
exciter,
this
voltage
is
monitored
and
when
a
user
set
limit
is
reached
the
exciter
automatically
switches.
If
using
one
of
the
iboc
modes
there
are
status
lines
that
come
from
the
exciter
to
tell
the
controller
if
the
transmitter
should
be
in
class
C
or
class
AB.
When
the
exciter
switches
to
one
of
the
three
modes,
FM,
FM+HD
or
HD
Only,
the
controller
sets
the
proper
power
supply
voltage,
sets
the
PA
modules
to
the
correct
class
of
operation
and
loads
the
calibration
points
for
forward
and
reflected
power
in
the
system
and
power
blocks
(FAX20/30/40).
Keep
in
mind
if
using
multiple
modes
of
operation
that
each
mode
requires
calibration.
The
transmitter
sends
a
mute,
APC
and
Exciter
active
line
back
to
the
on
‐
air
exciter.
The
mute
line
can
be
set
to
active
hi
or
low
depending
on
dipswitch
settings.
The
APC
voltage
is
on
the
range
of
0
to
4
VDC,
if
using
a
non
‐
Harris
Broadcast
exciter
the
exciter
input
must
be
compatible.
See
the
APC
description
in
Section
4.1.6,
System
APC
Summary of Contents for Flexiva FAX 5KW
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