Related Special Functions; Alc Ofr; Attenuator Range Hold On - HP 8642A Operation And Calibration Manual

Operation
Amplitude
Related
Special
Functions
Related
Operating
Instructions
3-74
Model 8642A/B
(cont'd)
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 accur;tcy is ±2 dB when ALe 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 ALe loop controls signal
amplitude. This produces a 30 dB range with monotonic, step-to-step amplitude
incremen ts.
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 -7 6) is a graphic
summary of this table. Refer to Table 1-1 (page 1-7) for AM and output amplitude
specifica tions.
The following functions are not possible when Attenuator Range Hold is enabled:
ALe
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-Iock messages.
219. Re-enable Settling. This special function re-enables the settling that is disabled
when Special Function 119 is selected.
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 3-165) for information about the way these are
accessed.