Operation
Model 8642A/B
Modulation, Pulse (cont'd)
Mixed Modulation
The Signal Generator can simultaneously modulate the RF signal with more than one
modulation type. The Signal Generator does not allow simultaneous AM and pulse
modulation or FM and <J>M. Pulse modulation is allowed in the following
combinations:
Either
• Internal pulse modulation or
• External dc-coupled pulse modulation
With any one of the following:
• Internal FM,
• External ac- or dc-coupled FM,
« Internal + external ac- or dc-coupled FM,
« External low rate FM (Special Function 5),
• Internal + external low rate FM (Special Function
1
12),
• Internal $M,
® External ac- or dc-coupled 4>M, or
9 Internal + external ac- or dc-coupled $M.
NOTE
All internal modulation sources use the internal modulation
oscillator, therefore all internal modulation, as well as MOD
OUTPUT, will have the same modulation frequency.
Related
Special
Functions 113. Modulation Frequency Correction Off. This special function disables the
single-band calibration of the modulation frequency oscillator that normally occurs
whenever the modulation oscillator frequency is set or the internal modulation
oscillator is put into use. When this calibration is disabled, the typical modulation
frequency switching time is decreased by approximately 200 ms. For more
information, refer to "Speeding Up Modulation Switching Time" on page 3-1 32.
213.
Modulation Frequency Correction On. This special function re-enables the
modulation frequency correction disabled with Special Function 11 3.
248.
Calibrate the Modulation Frequency Bands Again. This special function enables
you to initiate the calibration sequence that normally only occurs during instrument
power-up. This function can be used, for example, to recalibrate the modulation
oscillator frequency bands if normal modulation frequency correction has been
disabled with Special Function 11 3. Calibration typically takes one to two seconds.
Related
Operating
Instructions Refer to Modulation Oscillator (page 3-131) for more information on the internal
modulation oscillator that is the common source for all internal modulation as well as
for the MOD OUTPUT connector.
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.
3-130
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