Field Service Procedure – Replacement Pol Pot Kit, USAT
Page
1
of
7
Document No
135929 Rev A
Copyright © Sea Tel, Inc 2012 - The information contained in this document is proprietary to Sea
Tel, Inc. This document may not be reproduced or distributed in any form without prior written
consent of Sea Tel, Inc.
1.
Brief
Summary:
Troubleshooting
document
for
diagnosing
a
fault
with
and
replacing
the
pol
pot
on
the
USAT
series
antennas.
2.
Checklist:
Verify
Range
of
Motion
Verify
Pot
Feedback
Measure
Resistance
3.
Theory
of
Operation:
A
polang
potentiometer
is
used
to
provide
a
feedback
reference
for
the
position
of
the
feed
assembly
for
linear
polarization.
The
pot
acts
as
a
potential
divider
giving
an
output
voltage
which
varies
from
0VDC
to
5VDC
throughout
the
feed
assembly’s
180
degree
range
of
motion.
The
PCU
converts
the
voltage
output
from
the
pot
into
the
numerical
value
displayed
on
the
DAC.
A
failure
with
the
pot
causing
it
to
output
an
incorrect
voltage
will
result
in
the
feed
assembly
not
being
aligned
correctly
causing
bad
cross
pol
isolation.
One
indication
that
there
is
a
fault
with
the
feed
alignment
of
the
system
is
that
the
target
light
will
be
permanently
illuminated
on
the
DAC
and
the
antenna
won’t
target
correctly.
It
will
sit
8
degrees
above
the
satellites
elevation
look
angle.
As
part
of
the
antennas
targeting
procedure
the
system
will
target
8
degrees
above
the
satellite,
calculate
the
auto
threshold
setting
based
on
the
noise
floor
level
and
then
align
the
feed
for
the
correct
reception
position
based
on
the
vessels
GPS
location
and
the
lookup
table
in
the
DAC.
If
the
system
is
unable
to
drive
the
pol
motor
to
obtain
the
correct
feedback,
or
if
the
pot
has
failed
and
won’t
give
the
correct
feedback,
the
antenna
can’t
complete
the
target
process
and
the
antenna
will
stay
in
this
position.
Setting
the
pol
type
to
“0009”
will
make
the
antenna
target
by
removing
the
auto
pol
function
from
the
targeting
process;
however
the
miss
alignment
of
the
feed
will
cause
bad
cross
pol
isolation.
4.
Verify
the
Range
of
Motion:
*Note:
Do
not
try
to
drive
the
polarity
of
the
antenna
using
the
pol
window
of
the
DAC,
remote
commands
must
be
used.
Also
no
update
on
the
pol
value
will
be
displayed
on
the
DAC
when
the
pot
is
rotated;
it
works
solely
from
drive
commands
entered
into
the
remote
command
screen.
First
verify
the
settings
in
the
DAC
are
correct,
the
pol
scale
should
be
set
to
0090
to
give
the
feed
180
degrees
of
motion.
The
default
pol
offset
setting
for
a
USAT
antenna
is
0030
(however
this
may
have
been
modified
slightly
to
“trim”
the
pol
angle).
Turn
tracking
off
(if
applicable)
and
drive
the
elevation
to
0
degrees
to
make
it
easier
to
view
the
feed
assembly
for
diagnostic
purposes.
Set
the
pol
type
in
the
setup
menu
of
the
DAC
to
“0009”
to
set
the
mode
of
the
pol
assembly
to
manual.
Now
enter
the
remote
command
window
(in
the
setup
menu)
and
input
the
command
“g0020”
to
drive
the
feed
assembly
to
its
lower
limit.
The
LNB
should
be
vertical,
to
the
left
of
the
OMT
with
the
coax
cable
pointing
downwards.
Now
drive
the
feed
to
its
upper
limit
by
inputting
“g0210”
into
the
remote
command
screen
of
the
DAC.
The
LNB
should
be,
vertical
to
the
right
of
the
OMT
with
the
coax
cable
pointing
upwards.
If
the
feed
doesn’t
have
the
full
180
degrees
of
rotation
verify
the
resistance
of
the
pot
as
per
the
following
procedure.
Summary of Contents for USAT
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