Comments - HP 8642A Operating Manual
Synthesized signal generator
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Also See for 8642A:
- Service manual (326 pages) ,
- Manual (636 pages) ,
- Operation and calibration manual (314 pages)
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Model 8 6 4 2 A / B
Operation
Modulation, AM (cont'd)
Comments
Specified AM Rates Can Be Increased by Selecting the Het Band
AM depths are specified for depths less than or equal to 90% a t a maximum rate of 20
kHz in bands 2, 3, and 4 (4.130860 to 33.046875 MHz). You can increase specified
AM rates in this RF frequency range from a maximum of 20 kHz to a maximum of
100 kHz by selecting Special Function 8 (Prefer Het Band). Refer to "How to Select
the Het Band" on page 3 - 4 1 .
Spurious Signals (Spurs) That Occur With the Internal Source
Internally generated spurs (with levels specified less than - 1 0 0 dBc) might be present
when the internal modulation oscillator is in use. These spurs will be eliminated when
no internal modulation source is modulating the carrier, and the modulation oscillator
(MOD OUT) is off.
Modulation Switching Time
The time required to turn on the internal modulation oscillator or to switch between
modulation frequencies can be reduced by approximately
200 ms (depending on
modulation frequency), with a loss in modulation frequency accuracy, by selecting
Modulation Frequency Correction Off (Special Function 113). For more information,
refer to "Speeding Up Modulation Switching Time" on page 3-1 32.
The time required to turn on the internal modulation oscillator is increased by
approximately 200 ms if DC FM Update Mode (Special Function 117) is active. For
more information, refer to "117. DC FM Update Mode On" (page 3-116).
Modulation Restrictions with Other Functions
AM and pulse modulation are not possible during amplitude sweep. Also, AM and
pulse modulation are not possible when ALC Off (Special Function 4) is selected.
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 simultaneous
FM
and
$M.
AM
is allowed
in
the
following
combinations:
Any one of these types:
•
Internal AM,
«
External a c - or dc-coupled AM, or
•
Internal + external a c - or dc-coupled AM
With any one of the following:
•
Internal FM,
•
External a c - or dc-coupled FM,
•
Internal + external a c - or dc-coupled FM,
•
External low-rate FM (Special Function 5),
•
Internal + external low-rate FM (Special Function 112),
©
Internal <t>M,
•
External a c - or dc-coupled <I>M, or
•
Internal + external a c - or dc-coupled <i>M.
NOTE
All internal modulation
sources use the
internal
modulation
oscillator,
therefore
all
internal
modulation, as well as MOD OUTPUT, have the same
modulation frequency.
3-101
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