1.5 Mhz If - HP 8901B Operation And Calibration Manual

Model 8901B Adjustments
Adjustment 12
FM DISTORTION AND INCIDENTAL AM
-
1.5 MHZ IF
0
Service Sheet
5
Description
The AMFM test source is frequency modulated at a 100 kHz rate with
400
kHz peak deviation. The
peak deviation is measured with both the positive and negative peak detectors when the Modulation
Analyzer is tuned first to the signal and then
to its image. The IF is adjusted so that the difference
between the detector readings is the same for both signals. This method permits proper adjustment of
distortion even in the presence of a small amount of distortion from the FM source. The incidental AM
is measured on an FM signal modulated at a 1 kHz rate and
50
kHz peak deviation. The instrument
is adjusted for minimum AM.
Equipment
AM/FM Test Source
.............................................................
H P 11715A
Audio Analyzer
...................................................................
HP 8903B
HP 8 9 0 1 B
MODULATION ANALYZER
HP 11715A
AM/FM TEST SOURCE
I
0
INPUT FYS4 OUTPUT
I
AUDIO
AUDIO ANALYZER
OUTPUT
Figure 5-5. FM Distortion and Incidental AM - 1.5 MHz Adjustment IF Test Setup
Procedure
1. Connect the equipment as shown in Figure 5-5. (The A M F M
test source output can be connected
2. Set the audio analyzer's oscillator to 100 kHz at
4V.
On the AMFM test source, set the test
3. On the Modulation Analyzer, press the blue key then press INSTR PRESET (the AUTOMATIC
4.
Tune the AM/FM test source's carrier frequency to approximately
400
MHz.
5. On the Modulation Analyzer, press MHz to center its tuning. Press FM. Adjust the audio
analyzer's oscillator level for a display of 400 kHz peak deviation on the Modulation Analyzer.
6. On the Modulation Analyzer, switch the DETECTOR between PEAK+ and PEAK- and note
the difference between the two readings. Adjust A18R23
(FM DISTN 1.5 MHZ IF) for equal
readings between PEAK+ and PEAK-.
either
to
a sensor module or directly
to
the Modulation Analyzer's INPUT.)
mode
to
FM.
OPERATION key) to preset the instrument. Set the
HP
FILTER
to
50 Hz.
Adjustment 12
5-19