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Section
IV
Model 339
A
TUNEABLE
NOTCH
FILTER
(
hp-
Model 339A)
Figure
4-8.
Oscillator Total
Harmonic
Distortion
Test.
Figure
4-9.
Logarithmic
Addition
of
Harmonic
Components.
Table
4-5.
Oscillator Total
Harmonic
Distortion
Test.
m.
Calculate
the
Total
Harmonic
Distortion using
the
graph
shown
in
Figure
4-9.
As
an example:
If
the
amplitude of
the
second
harmonic
is
—
110
dB
and
the
third
harmonic
amplitude
is
-
1
14
dB
the
dB
difference
between
the
two
is
-4
dB. Locate
this
number
on
the
horizontal
axis
of
the
graph.
The
-4
line intersects
the
curve
at
approximately
the
+1.5
level
on
the
vertical
axis.
The
total
harmonic
distortion
is
therefore the
amplitude
of
the
largest
harmonic
(2nd harmonic)
plus
the
number
determined
on
the
vertical axis
(-110 dB
+
1.5
dB
= -
108.5 dB).
n.
The 339A
should meet
the 10
Hz
THD
specification
listed in
Table
4-5.
o.
Repeat
Steps
f
through
m
for
each freqeuncy
listed
in
Table
4-5.
NOTE
It
may
be necessary
to
increase the
Bandwidth
of
the
Spectrum Analyzer
at
higher
frequencies.
Adjust
as
necessary
to
maintain
a
stable reading.
339A
Frequency
THD
Specification
10 Hz
>
-95
dB
100 Hz
>
-95
dB
1
kHz
>
-95
dB
10 kHz
>
-95
dB
20 kHz
>
-95
dB
30
kHz
>
-85
dB
50
kHz
>
-80
dB
109
kHz
>
-70
dB
4-20.
DISTORTION
ANALYZER
PERFOR-
MANCE
TESTS.
4-21.
The
Voltmeter
Performance
Tests,
at
the
beginning
of
this
section,
should be
performed and
the
Voltmeter accuracy
verified
before
proceeding with
the
Distortion
Analyzer
Tests.
4-22.
Fundamental
Rejection
and
Induced
Distortion Test.
4-23.
The
following
test
requires
an
exceptionally
low
4-8
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