If Bandpass Adjustment; If Bandpass Adjustment Setup - HP 8560A Service Manual

3. IF Bandpass Adjustment

Assembly Adjusted
A5 IF Assembly
Related Performance Test
Resolution Bandwidth Accuracy and Selectivity
Description
The center frequency of each IF bandpass filter pole is adjusted by DAC-controlled varactor
diodes and an inductor (for the LC poles) or a transformer (for the crystal poles). The
inductors and transformers are for coarse tuning and the varactors are for fine tuning by the
microprocessor. The inductors and transformers are adjusted such that the varactor diodes
are biased near the middle of their capacitance range. The varactor diode bias is measured
with the DVM.
Note
This procedure is not a routine adjustment. It should be performed only
if repairs to the A5 IF assembly are made. If the entire A5 IF assembly is
replaced, the assembly arrives pre-adjusted from the factory and requires no
further adjustment.
SPECTRUM
ANALYZER
Equipment
Digital Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DVM Test Leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Tuning Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2-20 Adjustment Procedures
BOARD
A 2
Figure 2-5. IF Bandpass Adjustment Setup
S K 1 5
HP 3456A
HP 34118A
8710-1010