HP 3048A Operating Manual page 42

Tuning Requirements
The Peak Tuning Range required for your measurement will
depend on the frequency stability of the two sources you
are using. The signals from the two sources are mixed in
the HP 11848A's Phase Detector to create a beatnote. In
order for the loop to acquire lock, the center frequencies
of the sources must be close enough together to create a
beatnote that is within the system's Capture Range. Once
the loop is locked, the frequency of the beatnote must
remain within the Drift Tracking Range for the duration of
the measurement. In Figure 2-3, the ranges calculated in the
previous example are marked to show their relationship to
the beatnote frequency.
DRIFT TRACKING
RANGE
•
1
CAPTURE
RANGE
10X OF THE PTR
20X OF THE PTR
100 Hz 200 Hz 1000 Hz
Figure 2-3. Relationship of Capture and Drift
Tracking Ranges to Beatnote Frequency
rev.UJUL88 Signal Source Fundamentals 2-5