HP 85325A Operating And Service Manual page 68

NOTE
Procedure
Figure 5-1
NOTE
Synthesized LO Source Timebase Check and Adjustment
You can adjust the internal timebase after reconnecting ac power for 30
minutes, but for best accuracy, test again after the instruments have been ON
or in STANDBY for 24 hours.
Frequency changes, due either to a change in orientation with respect to the
earth's magnetic field or to a change in altitude, are usually eliminated when
the instrument is returned to its original position. A frequency change due to
mechanical shock usually appears as a fixed frequency error.
1. Connect the equipment as shown in Table 5-1. Preset all instruments and
let them warm up for one hour.
LO Source 10 MHz Timebase Adjustment Setup
If the oscilloscope does not have a 50 ohm input impedance, connect
channel 1 and the Trig 3 input through a 50 ohm feed through. Ensure that an
external frequency standard is not connected to either of the synthesizers.
(At instrument preset the synthesizers automatically choose the external
standard as the reference if one is connected to the 10 MHz REF INPUT.)
2. On the oscilloscope, set:
Channel 1:
Display
Volts/Division
Coupling
Impedance
Channel 2:
Display
5-2 HP 85325A Operating and Service Manual
On
200 mV
dc
50 ohm
Off