Chapter 2 35
E4438C Vector Signal Generator Overview
Front Panel Display
MOD ON/OFF This annunciator indicates if the RF carrier is modulated (MOD ON while there is an
active modulation format), or if the modulation is off (MOD OFF). Either condition of
this annunciator is always visible in the display.
The MOD ON annunciator may be showing even when there are no active modulation
formats. This merely indicates that the carrier signal will be modulated when a
modulation format is enabled.
OVEN COLD This annunciator appears when the temperature of the internal oven reference oscillator
has dropped below an acceptable level. When this annunciator is on, frequency
accuracy is degraded. This condition should occur for several minutes after the signal
generator is first connected to line power. The annunciator is timed, and automatically
turns off after a specified period.
PULSE This annunciator appears when pulse modulation is turned on.
R This annunciator appears when the signal generator is remotely controlled over the
GPIB, RS-232, or VXI-11/Sockets (LAN) interface.
RF ON/OFF This annunciator indicates when the RF signal is present (RF ON) at the RF OUTPUT,
or if the RF signal is not present (RF OFF) at the RF OUTPUT. Either condition of this
annunciator is always visible in the display.
S This annunciator appears when the signal generator has generated a service request
(SRQ) over the GPIB, RS-232, or VXI-11/Sockets (LAN) interface.
SWEEP This annunciator appears when the signal generator is sweeping in list or step mode.
T This annunciator appears when the signal generator is in talker mode and is transmitting
information over the GPIB, RS-232, or VXI-11/Sockets (LAN) interface.
UNLEVEL This annunciator appears when the signal generator is unable to maintain the correct
output level. The UNLEVEL annunciator is not necessarily an indication of instrument
failure. Unleveled conditions can occur during normal operation. Two other
annunciators appear in the same position: ALC OFF when the ALC circuit is disabled
and BBG DAC when the waveform data exceeds the DAC range.
BBG DAC This annunciator appears when the waveform data exceeds the range of the DAC, which
causes a DAC over-range error. It remains illuminated until the condition is corrected by
scaling the data. It appears in the same location as the UNLEVEL and ALC OFF
annunciators, and is the dominant annunciator. For example, if an unleveled condition
exists at the same time as a DAC over-range condition, the DAC over-range annunciator
remains until corrected. Once corrected, the UNLEVEL annunciator appears.
UNLOCK This annunciator appears when any of the phase locked loops are unable to maintain
phase lock. You can determine which loop is unlocked by examining the error
messages.
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