Basic Measurements

Making SC/H Phase Measurements

(1750A---Series Only)

The SC/H display provides a vector display of the subcarrier- to-horizontal-sync phase relationship. The burst vector and the phase of the 50% point of the leading edge of sync are displayed.

NTSC

Dual-Dot Display

When REF is set to internal, the 1750A has a dual-dot SC/H display (Figure 4-6). The dots represent the 50% points of horizontal sync.

To make a measurement, align the burst vector as shown in Figure 4-6. The location of the horizontal sync dot is the SC/H phase of the signal. With the dual dots, SC/H phase range is limited to 180°, because the SC/H phase of a single signal referenced to itself can only vary ±90°. At 180°, the video signal again has a + field subcarrier phase sequence, making it “SC/H phased.”

Single-Dot Display

When REF is set to EXT, the 1750A has a single-dot display (Figure 4-7). This relative mode allows the comparison of two signals, the selected INPUT and EXT REF. The phase shift between the two subcarriers can extend from 0° to 360°.

A dot near 0° (relative to burst) indicates the input is perfectly SC/H-phased with the EXT REF input, and that the color frames are properly matched. A phase reading of 180° indicates that the INPUT and EXT REF color frames are not properly matched.

4-10

1740A/1750A Series Waveform/Vector Monitor User Manual