HP 8568B manual MHz Bandwidth Filter Adjustments, Frequency Zero Check

7. 3 MHz Bandwidth Filter Adjustments

Procedure 1. Position instrument upright as shown in Figure 3-37 and remove top cover.

2.Set LINE switch to ON and press ~NSTR PRESET).

Frequency Zero Check

3.Connect CAL OUTPUT signal to RF INPUT

4.Key in IRECALL) @.

5.Adjust front panel FREQ ZERO control for maximum signal amplitude on the CRT display.

Filter Center and Symmetry Adjustments

6.Key in ~CENTER FREQUENCY) 20 MHz, CFREQUENCY SPAN) 10

kHz, [REsBWI) 1 kHz, and press LIN pushbutton. Press

CREFERENCE LEVEL] and adjust reference level, using step keys and front-panel knob to place signal peak near top CRT graticule line.

7.On the A4A7 assembly, connect crystal filter bypass networks between the pins above C41 SYM, C32 SYM, C23 SYM, and Cl4 SYM.

8.Adjust A4A7C7 CTR for minimum amplitude signal peak. Adjust A4A7C6 SYM for best symmetry of signal. Repeat adjustments to ensure that the signal is nulled and adjusted for best symmetry. See Figure 3-38 for location of adjustments.

Note	You	may	find	it	helpful	to widen and narrow the frequency span of
	the	instrument		to adjust		the bandpass symmetry and centering for
	each	filter	stage.

A4A7

3 MHz B a n d w i d t h F i l t e r

A4A7

Figure 3-38.

Location of Center, Symmetry, and 10 Hz Amplitude

Adjustments

9. Remove crystal filter bypass network near Cl4 SYM.

Adjustments 3-73