HP 8642A Operation And Calibration Manual

Operation
Model 8642A/B
Modulation, FM (cont'd)
Related
Special
Functions
3-} 12
How to Obtain Low Residual FM
At high FM deviation settings, the residual FM performance of the Signal Generator can
be limited by ground loops set up between the external FM source and the Signal
Generator. For minimum residual FM, a floating external FM source should be used.
How
to Obtain Maximum PM Stereo Separation
Maximum stereo separation (at least 50 dB) is achieved in the heterodyne band with
dc-coupled FM. Lo's Distortion FM (Special Function 7) may be selected to further
red 11ce total harmonic distortion.
HP-IB. Sequence Dependency
FM settings are sometimes coupled with other functions. Therefore, HP-IE codes may
need to be entered in a particular sequence when accessing combinations of these
functions. Refer to the discussion about Sequence Dependency, which begins on page
3 - 1 2
in the HP - IE portion of this Section IlL
5.
112.
Table 3-20. Maximum FM Deviation Settings with only an External Source
Maximum FM Deviation Settings
(kHz per Volt)
Band
Frequencv Range (MHz)
Pre-Emphasis On
Pre-Emphasis Off
(Special Function 6)
10 1057.500001 to 2115.00000
3000.000 420.498
(8642B
only)
9
528.750001
to 1057.500000
1500.000 210.249
8
264.375001
to
528.750000
750.000 105.124
7 132.187501
to
264.375000 375.000
52.562
6 66.093751
to 132.187500 187.500 26.281
5 33.046876
to 66.093750
93.750 13.140
4 16.523438
to 33.046875 46.875
6.570
3
8.261719
to 16.523437
23.437 3.285
2 4.130860
to
8.261718
11.718 1.642
1 0.100000
to
4.130859
93.750 13.140
Het 0.100000 to
132.187500'
1500.000 210.249
'When FM deviations exceed limits listed for Bands 1 through 6. the Signal Generator automatically switches
to the Heterodyne Band
External Low Rate PM On
!nternal + External Low Rate PM On
These special functions typically provide 0.4 Hz. to 200 kHz external-FM ac coupling
witb the Signal Generator remaining in a phase locked stateo Input coupling required for
these functions makes the Signal Genera tor especially sensitive to de voltage flllct uatio lIS.
Relatively small dc voltage changes Gan cause the Signal Generator to lose phase lock,
requiring one to two seconds to regain the locked condition. These functions will be
turned off when another FM modulation source is selected.
205. External Low Rate FM Off. This special function turns off the roM modulation
source selected with Special Function 5. When Special Function 5 is turned off in this
way, the Signal Generator selects external, ac-collpled FM

HP 8642A Specifications

General

Brand	HP
Model	8642A
Category	Inverter
Language	English