Reducing
A
veraging
Bandwidth
In
this
example
you
will
use
the
averaging
lter
control
to
observe
low-level
narrow-band
signals
close
to
the
noise
oor
.
The
averaging
lter
is
a
post-detection
low-pass
lter
that
smooths
the
displayed
trace
.
When
signal
responses
near
the
noise
level
of
the
receiver
are
visually
masked
by
the
noise
,
the
averaging
lter
can
be
narrowed
to
smooth
this
noise
and
improve
the
visibility
of
the
signal.
(Reducing
averaging
bandwidth
requires
a
slower
sweep
time
to
keep
the
receiver
calibrated.)
Using
the
averaging-bandwidth
function,
measure
the
amplitude
of
a
low-level
signal.
1.
As
in
the
previous
examples
,
connect
an
antenna
to
the
receiver
input.
Set
the
receiver
to
view
a
low-level
signal.
2.
Reduce
the
IF
bandwidth
by
pressing:
4
BW
5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
IF
BW
AUTO
MAN
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30
4
kHz
5
3.
Reduce
the
averaging
bandwidth
by
pressing:
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
AVG
BW
AUTO
MAN
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100
4
Hz
5
This
improves
the
display
of
the
signal
by
smoothing
the
noise
,
allowing
better
measurement
of
the
signal
amplitude
.
A
\# "
mark
appears
next
to
the
AVG
BW
annotation
at
the
bottom
of
the
screen,
indicating
that
the
averaging
bandwidth
is
not
coupled
to
the
IF
bandwidth.
6-26
Making
EMI
Diagnostic
Measurements