HP 8901B Operation And Calibration Manual page 416

Model
8901B
Adjustment 16
HP 89016 ( S t e p 4 )
I
MODULAT I ON ANALYZER
Adjustments
OUTPUT
FM DISTORTION AND INCIDENTAL AM
-
455 KHZ IF
0
Service Sheets
5
and
8
I
!
I N P U T
? l ; u &
( s t e p 1 )
Description
M O D U L A T I O N
OUTPUT/
: E 8
0
( S t e p
4 1 I N P U T
-
AUDIO
I N P U T
AUDIO ANALYZER
; ; : E ;
000000
O
0000
0
0 0
0
0 0
0 0 0 0 0 0 0
0000
0
The signal generator is set to
2.45
MHz and frequency modulated at a 1 kHz rate with 10
kHz
peak
deviation. The incidental AM on the signal is measured and the instrument is adjusted for minimum
AM. At
2.45
MHz the signal is not down converted by the Modulation Analyzer but goes directly into
the IF. The adjustment alters the rolloff characteristic of a
2.5
MHz IF low-pass filter, which is the
principal source of the incidental AM.
For the
455
kHz
IF,
the AM/FM
test
source is frequency modulated at
a
10
kHz rate
with 10 kHz
peak deviation. The demodulated FM is measured with a distortion analyzer and FM distortion is
adjusted for a minimum. The incidental AM is measured with FM set for a 1
kHz rate and
5
kHz
peak
deviation. The instrument is adjusted for minimum AM.
Equipment
AMFM Test Source
.............................................................
HP 11715A
Audio Analyzer
...................................................................
HP 8903B
Signal Generator.
.................................................................
HP 8640B
SIGNAL GENERATOR
r
HP 1 1 7 1 5 A
AM/FM TEST SOURCE
I
FW3Z
OUTPUT
r l
: o o : o
AUD I O
I N P U T
Figure
5-7.
FM Distortion and Incidental AM
-
455 kHz IF Adjustment Test Setup
Procedure
NOTE
In the following procedure the RF modulation source can be connected
either to a sensor module (which i s connected to the Modulation Analyzer)
or directly to the Modulation Analyzer's INPUT connector. The procedure
i s written for the latter case.
1. Set the signal generator to
2.45
MHz at
0
dBm with 10 kHz peak FM deviation at a
1
kHz rate.
Connect its RF output to the Modulation Analyzer's INPUT as shown in Figure
5-7.
2.
On the Modulation Analyzer, press the blue key and then press INSTR PRESET (the
AUTOMATIC OPERATION key)
to
preset the instrument. Key in
34.0
SPCL
to
measure the
IF frequency. The IF should be approximately
2.45
MHz. If it reads approximately
0.455
MHz,
tune the frequency down slightly until a reading of
2.45
MHz is obtained.
Adjustment 16
5-25