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DIGITAL MODULATION MODE
3-17
Setting the digital modulation system
The
[Mod'n System]
key on the
Sig Gen
menu (Fig. 3-44) is used to select the modulation system
or type, set the channel filter characteristics and set the symbol data rate. User defined systems
can be created and stored for subsequent recall. Providing Test Tones has not been selected,
pressing the
[Mod'n System]
key causes the
Digital Modulation System Menu
shown in Fig. 3-9 to
be displayed. If Test Tones has been selected, the
Digital Modulation System Menu
shown in
Fig. 3-27 is displayed instead.
LOCAL
Symbol
Rate
Select
System
Select
Mod Type
Filter
Type
Filter
Alpha
Store to
USER "n"
C2432
Digital Modulation System Menu
Current System: NADC
Modulation Type :
/4 DQPSK
Symbol Size
: 2 bits
Symbol Rate
: 24.3000 kHz
Filter Type
: Root Nyquist
Filter Alpha
: 0.35 - - - -
π
Fig. 3-9 Digital modulation: Modulation system menu with NADC (D-AMPS) selected
Modulation type and system selection
The type of modulation to be generated can be set either by selecting a preset system (either
user-defined or predefined) using the
[Select System]
key or by defining the type of modulation
(FSK, GMSK, PSK, QAM,) using the
[Select Mod Type]
key. Symbol rate, filter type and filter
bandwidth may also be specified. System selection is summarized in Fig. 3-10.