Video Filter Operation

Fig. 2-10. 1 MHz MARKERS OUT (Phase lock reference) connector.

DISPERSION 1 MHz/div.

d. Adjust the DISPERSION-CAL for 1 marker/division.

Use the Horizontal POSITION control or the IF CENTER FREQ

control to align the markers to the graticule lines. Dispersion

is calibrated over the center 8 divisions of the display. See

Fig. 2-10.

Video Filter Operation

The video filter restricts the video bandwidth so that noise

or beat signals are reduced. This application is very useful

when analyzing signals close to minimum resolution band-

width. Fig. 2-11 shows the apparent increased resolution

when the VIDEO FILTER is turned on. It does restrict the use-

able sweep rate, because of the filter time constant, to about

50 ms/div or slower.

Fig. 2-11. Integrating the display with the video filter.

The SQ LAW (power) position provides a display that is

Vertical Display Modes

approximately

proportional to the square of the input sig-

nal amplitude.

The display, therefore, approximates the input

The appearance of the displayed signal depends to a

signal power.

This is basically an expansion circuit to ac-

great extent on the setting of the VERTICAL DISPLAY switch.

centuate small

amplitude differences.

For example; to accentuate the side lobes of a signal, the

LOG (40 dB full screen) position should be used, as com-

pared to the SQ LAW (13 dB full screen) position. Fig, 2-12

Selecting the Sweep Rate

illustrates the effect of each display mode or each position

The sweep rate for wide dispersion coupled resolution set-

of the VERTICAL DISPLAY switch.

tings is usually set just above the visual flicker setting; how-

The LOG position increases the dynamic range of the dis-

ever, as the DISPERSION is decreased the sweep rate will

play by attenuating large amplitude signals more than small

begin to affect the resolution and sensitivity of the analyzer,

amplitude signals. This produces a display which approxi-

as described under Obtaining Optimum Resolution. There-

mates a logarithmic response curve. The circuit is basically

fore, as the DISPERSION settings are reduced the sweep

a compression circuit, and is most effective when there are

rate should also be reduced to maintain sensitivity and resolu-

large signal amplitude differences.

tion.

2-12