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Model
339A
Section
IV
Figure
4-10.
Fundamental
Rejection
and Induced
Distortion Test.
distortion signal source. In
most
cases the
Model 339A
being used
as a
source
will
be
sufficient.
However,
if
the
instrument
under
test
does
not
meet
the
Induced
Distortion
specifications
listed in
Table
4-6,
it
must
be
determined whether
the distortion
is
due
to
the signal
source or
the
analyzer
under
test.
In
some
cases
this
may
be accomplished
by exchanging
the signal
source with
another.
If
this
is
not
practical,
low-pass
filters
may
be
^nstructed
to
enhance
the signal purity of the source.
a.
Set the
339A
controls as follows:
FUNCTION
INPUT LEVEL
FILTERS
OFF
(out)
METER
RESPONSE
NORMAL
INPUT
RANGE
3
V
INPUT/GND SELECT
....
DIS.
AN./_L
(center position)
FREQUENCY
10
Hz
(1.0
x
10)
b.
Connect
the
equipment
as
shown
in
Figure
4-10.
c.
Set the
Low
Distortion Oscillator
for
an
output
frequency
of
10
Hz. Adjust
the
output
level
for
a
full-scale
(0
dB) meter
indication
on
the
339A
under
test.
d.
Adjust
the
frequency
of the Synthesizer
(3330B)
for
a
maximum
level
indication
on
the
Spectrum
Analyzer
M571A).
Enter
this
frequency
as
both
the
output
^Piuency
and
step
frequency
of the
synthesizer.
NOTE
When
adjusting
the
frequency
of
the
Synthesizer, use
frequency
steps
equal
to
10
%
of
the
fundamental
frequency being measur-
ed.
This insures
adequate
resolution.
e.
Reference
the
Spectrum
Analyzer
to
this level
by
pressing the enter
offset
button.
The Spectrum
Analyzer
should
indicate
00.00 dB.
f.
Set the
FUNCTION
switch of the
339A
under
test
to
DISTORTION.
g.
Adjust
the
DISTORTION
RANGE
control
for
an
on-scale
meter
indication
as
near
full-scale
as possible.
h.
Determine
the
fundamental
rejection
of
the
339A
under
test
by adding
the display
reading
of the
Spectrum
Analyzer
and
the distortion
range
setting
of the
339A
under
test.
(As
an example:
If
the
339A
DISTORTION
RANGE
control
is
set
to -80
dB
and
the
Spectrum
Analyzer
display
indicates
-35
dB
the
fundamental
rejection
is
-115 dB.)
i.
The
fundamental
rejection
level
determined
in
the
previous
step
must meet
or
exceed
the specification
listed
in
Table
4-6.
j.
Step
the
Synthesizer
frequency
to
the
second
harmonic
frequency.
4-9
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