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The Tuning Qualifications
Changing the PTR is accomplished by changing the VCO
Voltage Tuning Range value or the VCO Tuning Constant
value or both. There are several ways this can be done.
However, when considering these or any other options for
changing the PTR, it is important to remember that the VCO
source must always meet the following tuning qualifications.
■ The tuning response of the VCO source must always
remain monotonic.
■ The VCO source's output level must remain constant
across its tuning range.
As long as these qualifications are met, and the HP 3048A
does not indicate any difficulty in establishing its calibration
criteria, an increase in PTR will not degrade the system's
measurement accuracy.
The following methods may be considered for increasing or
decreasing the PTR.
Voltage-Controlled-Oscillators
1. Select a different VCO source that has the tuning
capabilities needed for the measurement.
2. Increase the Voltage Tuning Range of the VCO source.
Caution
Be careful not to exceed the input voltage limitations of the
Tune Port on the VCO source.
3-152
Signal Source Applications
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