HP 70908A, Service Manual

Page: 172 / 335

A djustment 12. 2nd Converter LO F eedthrough
The purpose of this adjustment procedure is to measure the 3.3 GHz 2nd LO feedthrough power
at the 2nd converter 321.4 MHz IF OUTPUT .
Note
Before performing this adjustment, verify completion of the following:
A djustment 11. V CO 2nd LO Frequency/Amplitude
1. Set the mainframe line switch to OFF .
2. Remove the HP 70908A RF section from the mainframe .
3. Install the extender module in the mainframe and connect the HP 70908A RF section to the
extender cable .
4. Connect the equipment as shown in Figure 7-25.
5. Set the mainframe line switch to ON and allow at least 30 minutes initial warmup before
starting the adjustment.
6. Load and run A djustment 12. 2nd Converter LO F eedthrough. Refer to Chapter 2 for
information about running the software .
The calibrated spectrum analyzer connects to the 2nd converter A8J2, 321.4 MHz IF OUT .
(Refer to the A9 2nd converter PLL replacement procedure .) The HP 70900A/B local oscillator
source provides the 300 MHz reference .
The calibrated spectrum analyzer setup is 3.3 GHz center frequency , 10 MHz span. The
spectrum analyzer measures 2nd LO feedthrough which can range between limits of 029.0 dBm
and 065.0 dBm.
Adjustment Procedures 7-33