HP 8568B 7.3 MHz Bandwidth Filter Adjustments, Figure 3-37.3 MHz Bandwidth Filter Adjustments Setup

7.3 MHz Bandwidth Filter Adjustments

Reference

Related Performance Test

Description

IF-Display Section

A4A7 3 MHz Bandwidth Filter

Resolution Bandwidth Switching Uncertainty Test

Resolution Bandwidth Selectivity Test

With the CAL OUTPUT signal connected to the RF INPUT, the 18.4 MHz oscillator can be adjusted with the FREQ ZERO control (on the front panel) to peak the IF signal for maximum amplitude for the center of the 3 MHz bandpass. Each of the five stages of the 3 MHz Bandwidth Filter is adjusted for bandpass centering and symmetry. Four crystal filter bypass networks are required for alignment of the filter stages. See Figure 3-91 for information concerning the bypass networks.

A stable 21.4 MHz signal is then applied to the IF section of the instrument from a frequency synthesizer. Each of the first four stages of the 3 MHz Bandwidth Filter is peaked in a 10 Hz bandwidth using an oscilloscope display. The final stage is peaked using the spectrum analyzer CRT display.

After all five filter stages are adjusted for centering, symmetry, and peaking, the CAL OUTPUT signal is used to match the 10 Hz and 1 kHz bandwidth amplitudes.

SPECTRUM ANALYZER f 3

Figure 3-37. 3 MHz Bandwidth Filter Adjustments Setup

Equipment Frequency Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . HP3335A Oscilloscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HP 545OlA Crystal Filter Bypass Network (‘t required) See Figure 3-91 Test Cable: BNC to SMB snap-on . . . . . . . . . . HP 85680-60093

3-72 Adjustments