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

 

 

 

 

BOARD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A:

 

 

 

 

 

 

 

 

 

S K 1 5

A 2

 

 

 

 

 

 

 

 

 

 

Figure 2-5. IF Bandpass Adjustment Setup

Equipment

Digital Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

DVM Test Leads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Special Tuning Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

HP 3456A HP 34118A 8710-1010

2-20 Adjustment Procedures