HP 8340B Manual page 82

4-16.
FM ACCURACY AND FLATNESS (Cont'd)
9. Press
[SHIFT] [CW]
on the DUT. Note the
CW
frequency shown
in
the ENTRY DISPLAY. This
activates the fine
tuning feature on the DUT.
The CW
frequency
will be displayed in the
DUT's
ENTRY
DISPLAY. Take
note of the flashing cursor
in the
ENTRY
DISPLAY. Press the STEP UP or
STEP DOWN keys to place the flashing cursor just to the left of the decimal
point. Turn
the
DUT's
rotary knob (changing the CW frequency)
until
the marker
on the HP 3585A's CRT dips. (It
is
normal for
a
spurious
signal to be
displayed below the actual marker. Keep
turning the DUT's
knob until the marker
dips.)
Press the STEP UP key twice. Turn the DUT's rotary knob
until
the marker on the HP 3585A
reaches minimum amplitude. This should
be possible every
75
MHz
or so due to the length of the
delay
line.
NOTE
Step
15
will instruct the operator to
set the DUT's FM sensitivity to 10
MHz/V when
performing step
10. If
the
HP 355D step
attenuator
has not
been set
to 50 dB, the DUT's OVERMOD light
will
come
on.
10.
Move the output of the HP 8447F to the DUT's FM
input.
Turn FM ON and AM
OFF. Verify that the
DUT's FM sensitivity
is set to
1 MHz/V
(default
condition).
11.
Set the HP 3585A
to
2 dB/DIV
and turn
A-B back ON. Press [CLEAR A]. Press [REF LVL] and
turn
the HP 3585A's
rotary knob (usually counter-clockwise)
until
the
marker
is on the
center
horizon¬
tal graticule. If the OVER RANGE beep and message
occur, turn the rotary
knob in the opposite
direction. Don't be
concerned
if
the marker does not move at
first,
it
may take several complete
turns of the rotary knob before
any
change is noticed on the
CRT.
12.
Press
[CONT] sweep on the HP
3585A. The spectrum analyzer will now display the FM flatness
from 50 kHz to 10
MHz.
The
HP 3585A's marker offset feature
can be used to display
a
digital
readout of the signal
power
level.
The readout will be
expressed relative to the
power
level at
100 kHz.
To
activate this
feature,
press the following keys on the HP 3585A:
[MANUAL]
[1] [0]
[0] [kHz] [OFFSET] [ENTER OFFSET] [MARKER]
The power
level at
any chosen frequency between 50 kHz and 10
MHz
(relative
to
the 100
kHz
power
level)
will be displayed in
the
upper
right hand
corner
of the
CRT. Turn
the HP 3585A's
rotary knob to
change the measurement frequency.
13.
Determine the maximum and minimum deviation
points from the 100
kHz
reference.
The
dif¬
ference between these points should be :s3 dB. Record the
worst case power level on the Test
Record Card.
14.
Repeat Steps
6
through
13
for frequencies of 2.5,
6.9,13.4,
and 18 GHz. If testing an HP 8341B,
proceed to step
15.
If testing an HP 8340B,
also
perform the following: Press
[CW] [2] [0] [GHz]. Repeat
steps
6
through
13.
15.
Repeat Steps
6 through 14 with the HP 355D step attenuator set to 50 dB. When repeating step
10,
set the FM
sensitivity to
10
MHz/V, not
1
MHz/V.
HP 8340B/41B
Performance Tests
4-81/4-82