Fluke 6060B Instruction Manual page 213

OPTION
"651
LOW-RATE Fm
REQUIREMENT
FM
Droop
is
less
than 15% with
lO
Hz
external
square
wave
modulation.
REMARKS
When
using the
RF
Spectrum Analyzer
as
an
FM
demodulator
using slope detection,
it is
important
to
operate the
RF
Spectrum
Analyzer detector
in
a
linear range.
This can be
checked by stepping
the
UUT
frequency
up
5
kHz
and then
down
5
kHz
from
the
operating point
and noting
that the display
moves
equal amounts.
If
it
doesn't,
tune the
RF
Spectrum Analyzer
slightly
and check for linearity again.
TEST
EQUIPMENT
Low-Frequency
Synthesized Signal
Generator
(LFSSG)
RF
Spectrum Analyzer
PROCEDURE
1.
Remove
the
Generator top
and
the Synthesizer
module
plate covers,
2
.
Connect
the
LFSSG TTL
output through
a
604-ohm
resistor
and
a
320 uF,
6V
capacitor
to
the
UUT
MOD
INPUT.
Thi.s
provides
a
square
wave
approximately
2V
p-p
at the
Generator's
MOD
input.
.1
Program
the
LFSSG
to 10
Hz
and any
level
around
IV.
4.
Program
the
UUT
to the
[RCL]
[9][8]
and 3-kHz
deviation,
This provides a 300-
MHz
signal at
-10 dBm.
5.
Connect
the input of the
RF
Spectrum Analyzer to the
UUT RF OUTPUT,
Set
the
RF
Spectrum Analyzer
so that the signal response
is
at
the
top of the display
using
linear detection.
6.
Program
UUT
for
EXT
FM.
7.
Using
a
lO-kHz Resolution
Bandwidth and
zero
Span/Div,
adjust either
the
Generator frequency
or the
RF
Spectrum Analyzer tuning for slope detection to
obtain a .square-wave
display.
Adjust
Time/Div and
Trigger
a.s
nece.ssary
to
obtain a stable
square-wave
display.
8.
Verify that the
droop of the
demodulated
FM
is
less
than
1
5%. For example,
if
the displayed
square-wave amplitude
(vertical
edge)
is
3.4 divisions, then the
droop
should be
less
than 0.51 divisions (0,15
x
3,4).
651-5.
ADJUSTMENT
TEST
EQUIPMENT
DMM
PROCEDURE
The
Offset
adjustment
(A2A9
R4)
is
set
to
OV,
1.
Program
UUT
to
[RCL]
[9][8]
and
9.99
kHz
deviation,
and
set
the rear panel
EXT/INT
FM
switch
to
EXT,
with
no
external
modulation signal applied.
651-2