To prepare a QAM or DVB QAM measurement
This task shows you one way to set up a QAM or DVB QAM measurement.
The task uses the RF section (0-10 MHz) receiver and a 32 DVB QAM
signal from the signals disk. Several other tasks in this chapter use this
setup to teach you how to use video demodulation.
1. Initialize the analyzer:
Press [
Instrument Mode
], [
receiver
], then press:
89410A: [
input section (0-10 MHz)
].
89441A: [
RF section (0-10 MHz)
].
Press [
Preset
].
Press [
Instrument Mode
], [
vector
].
Press [
System Utility
], [memory usage], [configure meas memory)], [max time pts], 4096.
2. Supply a 32 DVB QAM signal to the channel 1 INPUT or perform the following
steps to load a 32 DVB QAM signal from the Signals Disk into a data register
and play it through the analyzer’s aribtrary source:
Insert the Signals Disk into the internal disk drive.
Connect the SOURCE to the channel 1 INPUT.
Press [
Save/Recall
], [
default disk
], [
internal disk
].
Press [
Return
], [
catalog on].
Rotate the knob to highlight 32DVBQAM.DAT
Press [
recall trace
], [
from file into D1
], [
enter
].
Press [
Source
], [
source on], [source type
], [
arbitrary
].
3. Select the optimum range:
Press [
Range
].
Press the down-arrow key until the Channel-1 Over and Half LEDs are on.
Press the up arrow key one press at a time until the Over LED turns off.
For additional details about selecting the optimum range, see online help
for the [
Range], [ch1 range] softkey.
4. Select a center frequency and span:
Press [
Frequency
], [
center
], 5, [
MHz
]
Pr ess [
span
], 2.5, [
MHz
].
The center frequency tunes the analyzer to the carrier frequency. To
obtain reliable carrier lock, the center frequency must be close to the
carrier frequency. For details, see ‘’Carrier Locking’’ in the
Video Demodulation Concepts (Opt. AYA) chapter.
Selecting the correct frequency span is also important when using video
demodulation. The span must be wide enough to include all signal
components, and yet not too wide, or the measurement may be affected
by excessive noise and slower speed. For details, see ‘’Parameter
Interactions’’ in the Video Demodulation Concepts (Opt. AYA) chapter.
Using Video Demodulation
(Opt. AYH)
9 - 8
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