The
app earance
of
signals
pro
vides
a
third
clue
ab out
their
origin.
Am
bien
t
signals
often
ha
v
e
c
haracteristic
app earances,
as
do
emission
from
man
y
devices
b eing
tested.
See
Figure
4-19.
Figure
4-19.
Characteristic
Appearance
of
Radiated
Emissions
The
conclusiv
e
w
a
y
to
distinguish
b et
w
een
ambien
t
and
emitted
signals
is
to
turn
o
the
EUT.
If
the
signals
disapp ear,
they
w
ere
b eing
emitted
b
y
the
EUT.
See
Figure
4-20.
Figure
4-20.
Equipment
Under
T
est
(EUT)
Turned
Off
As
an
additional
complication
in
making
radiated
measuremen
ts,
some
regulatory
test
pro cedures
require
the
EUT
to
b e
rotated
4-30
Making
Typical
Measurements
HP
8572A
EMI
Receiv
er
User's
Guide
