Section-4 Theory
October 28, 2013
4
‐
4
Copyright
©2013,
Harris
Broadcast
WARNING:
Disconnect
primary
power
prior
to
servicing.
888
‐
2720
‐
001
Figure 4-3 FAX5 Drive Chain
4.1.3
FAX20 RF Block Diagram
The
FAX20
contains
two
10
kW
power
blocks
in
one
cabinet.
One
power
block
contains
the
Micro
Module
controller,
the
other
power
block
has
only
a
LED
Status
board.
Figure
4
‐
4
is
a
block
diagram
of
the
RF
of
the
FAX20.
Figure 4-4 FAX 20 RF Block Diagram
The
output
of
the
Exciter
switcher
drives
a
2
‐
way
splitter.
This
splitter
is
a
3
dB
Hybrid
type
and
one
output
port
has
a
90
°
phase
shift.
The
power
blocks
each
have
a
0
°
phase
shift
which
allows
for
the
correct
phasing
at
the
power
block
combiner.
The
6
kW
power
block
combiner
reject
load
is
sized
to
accept
half
the
total
RF
in
the
case
where
one
power
block
is
off.
Exc A
Exc B
Rear
Panel
J4
J5
IPA/PA0
Module
RF Switch Bd
J3
J2
J7
IPA RF Level
To Sys Inf
To 7-Way
Splitter
PA BackPlane
RF Switch Bd
RF Switch Bd relays switch in
tandem. For FAX20/30/40 All IPA’s
will be on A or B
3 dB Pad provides isolation between
Exciters and IPA and helps prevent
overload of IPA
IPA RF Level Detected on
RF Switch board, it is DC
voltage used for IPA RF
Fault and switching
A
B
Exciter power displayed
on FAX is a DC Voltage
from Exciter. There is
no RF detector for
Exciter Power
J4
J5
J6
IPA/PA0 Module
uses one FET as
a IPA and one as
PA.
High Power Exciter
Low Power
Exciter
PB1
PB2
÷
Ʃ
Exciter
Drive
10 kW 0°
10 kW -90°
-3 dB @0°
-3 dB @ -90°
20 kW
Splitter on Multi-Unit
Interface Panel
3 dB Hybrid type
0° Phase shift through
power blocks, all splitters
and combiners are
Wilkinson type
3 dB Hybrid combiner
requires 90° Phase to
combine at the RF Output
6 kW
RJ
LD
Reject load
sized to ½
power of 1
power block
To calibrate
shut off 1
power block
for 100 %
Summary of Contents for Flexiva FAX 5KW
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