Service manual
Commercial
in
confidence
SMARTFIND
NAVTEX
service
manual
Page
23
When
reception
quality
is
good,
the
error
rate
will
be
low
(<4%).
The
error
rate
is
calculated
as
an
average
over
a
large
number
of
received
characters.
Wait
until
the
next
scheduled
transmission
time
of
a
distant
NAVTEX
station
(100
miles
or
more
away).
Use
the
monitor
facility
(receiver
options
page)
to
view
received
messages
as
they
are
received
in
real
time.
1.
Turn
off
all
sources
of
AC
power
usage,
battery
chargers,
inverters,
generators
and
shore
power.
Note
any
improvement
to
the
average
reception
error
rate.
2.
Turn
back
on
each
source
of
AC
power
usage,
one
at
a
time,
noting
any
increase
in
reception
errors
which
may
indicate
a
source
of
local
interference
worthy
of
further
investigation.
Reception
errors
may
also
be
caused
by
close
proximity
of
DC-powered
equipment.
In
this
case
repeat
the
above
test
but
include
all
DC-powered
instruments
on
board
as
well.
It
is
also
possible
to
monitor
for
locally
caused
interference
using
an
AM
band
radio
set
to
531kHz
or
SSB
set
tuned
to
the
appropriate
NAVTEX
channel.
Listen
to
the
general
‘on
channel
noise’.
Switch
off
equipment
until
the
general
noise
level
is
reduced
and
then
wait
for
a
transmission
to
see
if
there
is
an
improvement
in
reception.
Evaluating
antenna
location
When
the
antenna
is
situated
high
up
then
local
interference
should
be
reduced
as
it
will
be
most
distant
from
local
electrical
equipment
(sources
of
interference).
A
methodical
approach
when
evaluating
a
proposed
sensor
site
would
be
to
note
down
the
average
error
rate
from
each
station.
Then
make
a
change
to
the
proposed
sensor
location,
take
a
new
set
of
percentage
error
readings
and
consider
the
options.
Ideally
you
need
to
receive
from
at
least
one
distant
station
that
is
100
miles
or
more
away
or
you
may
find
it
impossible
to
get
any
received
error
count
at
all.
As
most
NAVTEX
stations
just
transmit
for
a
maximum
of
ten
minutes
at
a
time
in
every
four
hours,
you
will
have
to
work
quickly.
Alternatively,
take
your
time
and
make
a
new
set
of
readings
after
four
hours
has
elapsed.