Related Special Functions; Alc Off - HP 8642A Operating Manual

Operation
Model 8642A/B
Amplitude (cont'd)
Related
Special
Functions 4. ALC Off. This special function opens the output leveling loop to provide
(typically) a 5 dB improvement in third order intermodulation at a 2 kHz offset. Typical
output level accuracy is ±2 dB when ALC Off is selected.
204. Disable ALC Off. This special function re-enables the output leveling loop that
was disabled with Special Function 4.
9. Attenuator Range Hold On. When Attenuator Range Hold is selected, the Signal
Generator's output attenuators are fixed and the output ALC loop controls signal
amplitude. This produces a 30 dB range with monotonic, step-to-step amplitude
increments.
The upper and lower limits of each 30 dB range are determined by the Signal
Generator's output amplitude when Attenuator Range Hold is selected. Table 3-15 (on
the following page) lists each 30 dB range (in dBm) that is available (depending on the
output setting) when Special Function 9 is selected. This table also lists the ranges at
which amplitude and AM are specified (which are also dependent on the amplitude
setting when Special Function 9 was selected). Figure 3-9 (on page 3-76) is a graphic
summary of this table. Refer to Table 1-1 (page 1-7) for AM and output amplitude
specifications.
The following functions are not possible when Attenuator Range Hold is enabled:
ALC Off (Special Function 4), Pulse Modulation, and Amplitude Sweep.
209. Attenuator Range Hold Off. This special function turns off Attenuator Range
Hold that is selected with Special Function 9.
119. Disable Settling. This special function allows the Signal Generator's
microprocessor to respond to new commands without waiting for the internal circuitry to
settle. When using this special function, it's possible to select a function before the
previous function has finished settling. When settling is disabled, response time is
improved by up to 40 ms.. Special Function 119 disables out-of-lock messages.
219. Re-enable Settling. This special function re-enables the settling that is disabled
when Special Function 11 9 is selected.
Related
Operating
Instructions Refer to Relative Amplitude (page 3-77) for information on setting amplitude in units
other than dBm, V, mV, uV, dBuV, EMF V, EMF mV, EMF uV, or dB EMF uV.
Refer to Amplitude Sweep (page 3-83) for information on selecting an amplitude sweep
range up to 30 dB.
Refer to Knob (page 3-141) and Step, Increment Set (page 3-149) for information on
using these to modify settings.
Refer to Instrument Preset, Partial Preset (page 3-139) for information about setting
the instrument to an initialized state that maintains preset references including the
selected amplitude units.
Refer to Operating Messages (page 3-177) if the instrument displays a message you want
clarified.
Refer to Special Functions (page 3-16 5) for information about the way these are
accessed.
3-74