4
‐
1
888
‐
2720
‐
001
WARNING:
Disconnect
primary
power
prior
to
servicing.
Copyright
©2013,
Harris
Broadcast
FAX 5/10/20/30/40KW
October 28, 2013
Section-4 Theory
4
4.1
FAX Transmitter Configurations
The
following
theory
of
operation
is
intended
to
provide
a
general
overall
knowledge
of
how
the
FAX
high
power
series
(5
kW
through
40
kW)
of
transmitters
work.
The
FAX
series
of
transmitters
can
be
operated
in
any
one
of
three
modes,
which
are:
•
The
analog
FM
mode,
with
the
PA
modules
operated
class
C
mode
to
maximize
efficiency.
•
The
multiplex
mode
where
analog
FM
and
digital
(HD)
RF
signals
are
both
amplified
in
the
same
power
ampli
‐
fiers.
For
this
mode,
the
PA
modules
are
operated
class
AB,
because
digital
HD
requires
linear
amplifiers.
•
Digital
HD
mode
only.
For
this
mode,
the
PA
modules
are
operated
class
AB,
because
digital
HD
requires
linear
amplifiers.
The
10
kW
FAX
transmitter
is
the
basic
building
block
for
all
other
high
power
FAX
transmitters.
The
FAX10
does
not
contain
an
integrated
exciter
at
this
time
and
requires
an
exciter
external
to
the
transmitter
chassis.
All
FAX
transmitters
have
provisions
for
dual
exciters
with
internal
RF
switching.
All
of
the
current
Harris
Broadcast
FM
exciters
can
be
used
or
the
FAX
is
setup
to
allow
another
manufacturers
exciter
to
be
used.
The
5
kW
FAX
transmitter
has
the
identical
hardware
of
the
FAX10,
except
there
are
four
less
PA
Modules
and
three
less
PS
Modules.
The
5
kW
exciter
setup
is
slightly
different
than
the
10
kW
and
will
be
explained
in
the
5
kW
section.
A
20
kW
FAX
transmitter
consists
of
a
10
kW
transmitter
and
a
10kW
Power
Block
combined.
The
10kW
transmitter
is
referred
to
as
the
primary
power
block
or
power
block
1
because
it
contains
the
front
panel
LCD
Display
and
Multi
‐
unit
Interface
that
controls
the
overall
transmitter.
The
FAX20
is
housed
in
a
single
cabinet.
A
30
kW
FAX
transmitter
consists
of
a
10
kW
transmitter
and
two
10
kW
Power
Blocks
combined.
The
FAX30
is
housed
in
two
cabinets
with
a
cabinet
combiner
that
combines
them.
A
40
kW
FAX
transmitter
consists
of
a
10
kW
transmitter
and
three
10kW
Power
Blocks
combined.
The
FAX40
is
housed
in
2
cabinets
like
the
FAX30
4.1.1
10kW RF Block Diagram Description
Figure
4
‐
1
shows
the
RF
block
diagram
portion
of
a
FAX
10
kW
transmitter.
It
has
seven
PA
modules
and
one
IPA
module
that
have
identical
hardware
and
are
interchangeable
in
the
event
of
failure.
The
two
main
differences
between
the
PA
Module
slot
and
the
IPA
module
slot
is
the
IPA
uses
only
one
of
its
FET’s
and
the
other
as
a
backup
IPA.
The
other
difference
is
the
IPA
can
accept
the
APC
is
case
the
exciter
has
no
external
APC
input.
FAX
PA
Modules
consists
of
a
pair
of
RF
pallets
driven
and
combined
externally.
A
module
control
board
provides
simple
control
functions
including
turning
the
amplifier
on
and
off,
set
the
mode
of
operation
between
class
C
operation
for
FM
service,
and
class
A/B
for
digital
service
and
fault
monitoring
and
reporting.
Summary of Contents for Flexiva FAX 10KW
Page 2: ......
Page 8: ......
Page 10: ...WARNING Disconnect primary power prior to servicing ...
Page 167: ......
