HP 85020A Operating And Service Manual page 62

Service
Model 85020A/B
Preamplifier Adjustment Following Replacement of the Bridge
Microcircuit
Normally no adjustments are required on the 85020A/B Directional
Bridges. However, if the internal bridge microcircuit is replaced,
the adjustment described here should be performed to compensate
the preamplifier for the individual diode characteristics.
NOTE
Allow the equipment to warm up for 30
minutes before performing this adjustment.
Description
The input impedance and gain of the preamplifier assemblv are
Figure 8- 7. Preamplifier Assembly Adjustment Setup
Equipment
Scalar Network Analyzer ..... . HP 8756A
Sweep Oscillator ............. HP 8350A/B
RF Plug-In . ..... HP 83522A/83525A/B
Step Attenuator .... HP 8495A Opt. 001 (Calibrated)
50-Ohm to 75-Ohm Minimum Loss Pad
(85020B only) . HP 11852A