Agilent Technologies E4440A, Service Manual

Page: 60 / 436

60 Chapter 2
Overall Troubleshooting
Troubleshooting Using Front Panel Keys
ADC Ctrl
To view the dither signal, go to Basic mode, and set the span to 10 MHz.
ADC Dither
- Turns dither on and off.
ADC Dither CF
- Moves the dither center frequency in the IF. The
default is 11.25 MHz relative to 7.5 MHz (center of the screen). The
DAC range is 1 to 255.
ADC Offset (7, 3, 2, 1, 0)
- Provides an offset adjustment on the
NONE/direct ADC path or the manual gain path in the following
amounts:
These adjustments have a DAC range of 0 to 255. ADC Offset
adjustments are designed for factory use.
ADC Range
Auto
- The instrument automatically selects the proper ADC range
based on the ranging rules in firmware.
Auto Peak
- Allows the instrument to range up during a
measurement but not range down. Allows the ADC range to
automatically change to limit ADC gain (to prevent overdriving the
ADC). The ADC range cannot automatically change to allow more
ADC gain.
Auto Peak Lock
- Locks in one range setting. During a measurement
the ADC will not change ranges. ADC overloads could occur more
easily in this mode, but the fact that the ADC range is unchanged
improves the accuracy.
Manual
- Allows front panel control of the Auto range selections:
None, 0 dB, +6 dB, +12 dB, and +18 dB. The None setting bypasses
the ADC range circuits. When the ADC range is changed, the noise
floor level will increase with decreasing ADC gain values.
ADC Offset 7
offset adjustment on the NONE/direct ADC path
ADC Offset 3
offset adjustment on the 0 dB manual gain path
ADC Offset 2
offset adjustment on the 6 dB manual gain path
ADC Offset 1
offset adjustment on the 12 dB manual gain path
ADC Offset 0
(max gain)
offset adjustment on the 18 dB manual gain path