Section-4 Theory
October 28, 2013
4
‐
2
Copyright
©2013,
Harris
Broadcast
WARNING:
Disconnect
primary
power
prior
to
servicing.
888
‐
2720
‐
001
Referring
to
Figure
4
‐
1,
the
output
of
the
RF
Switch
board
feeds
a
2
‐
way
Wilkinson
splitter.
The
outputs
of
the
2
‐
way
splitter
in
turn
feed
two
7
‐
way
Wilkinson
splitters.
This
divides
the
IPA
output
by
14
equal
signals
to
feed
each
of
the
14
FETs
on
7
PA
modules.
The
RF
output
from
each
of
the
14
FETs
is
then
fed
to
the
14
‐
way
Wilkinson
combiner.
The
14
‐
way
combiner
also
houses
a
low
pass
filter
to
remove
any
harmonics
from
the
amplifiers.
Wilkinson
splitters
were
used
to
provide
better
isolation,
lower
loss
and
0
degrees
phase
shift.
This
phase
becomes
important
when
we
discuss
the
combining
of
the
power
blocks
in
the
FAX20/30/40.
The
output
of
the
LPF
then
goes
through
a
6
‐
port
directional
coupler
to
a
1
‐
5/8"
EIA
Unflanged
output
on
the
rear
of
the
transmitter.The
ports
on
the
directional
coupler
feed
the
controller
RF
sample
for
APC
and
VSWR
detection.
There
are
also
ports
for
modulation
monitoring
and
the
RTAC
signals
for
the
Flexstar
Exciter
Pre
‐
Correction
when
the
transmitter
is
running
in
Class
AB
mode.
Figure 4-1 FAX 10 kW Power Block
RF Output
through a
multi-loop
PA Module
PA Module
PA Module
PA Module
PA Module
IPA Module
PA Module
PA Module
Directional
PA Backplane
PA Backplane
PA Backplane
PA Backplane
IPA RF Switch Module
Exciter A RF Input
Exciter B RF Input
RF Input From IPA
High Level RF Switch
Coupler
Exciter Switch
Relay, on System
Interface Board,
2-Way
Splitter
Splitter
7-Way
Splitter
7-Way
Combiner/
14-Way
Splitter
PA System 2-Way
IPA RF Output to
LPF
Summary of Contents for Flexiva FAX 10KW
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