30 September 1988
To achieve an SC/H phase plant, the timing of sync becomes as important as
subcarrier, and each element should be viewed in that light. To aid video
tape editing, it is important to record video with proper SC/H phase and
also supply SC/H-phased reference to the machine in playback.
criteria do not have to be compromised with the system approach offered in
The SC/H phase is the time relationship between the subcarrier and the
leading edge of horizontal sync. A properly adjusted SC/H phase occurs when
the 50-percent points of the leading edge of sync and the subcarrier zero
crossing are coincident. The color frame pulse (V1) appears on line 11 of
field 1. V1 identifies field 1 of the 4-field color sequence.
The following test equipment is required to perform the SC/H phase
Equivalent test equipment may be substituted but
must be equal to or superior in performance.
a. Dual Trace Oscilloscope
AN/USM 425 (V) 1
(with delayed sweep and
one channel input inversion)
b. Switchable Delay Line
Subcarrier Delay DA
The following are test procedures used to measure the SC/H phase (figs
3-6 through 3-12).
a. Connect a video source requiring SC/H
phase measurement to the
inverting channel of the oscilloscope.
b. Connect subcarrier (3.58 MHz continuous) to the second channel of
c. While observing the oscilloscope (triggered at a horizontal rate),
adjust subcarrier to match amplitude of burst.
d. At the oscilloscope, invert the video display and set mode to
Figure 3-6 shows inverted video (top) and continuous
e. Adjust the oscilloscope for A plus B mode.
f. Adjust subcarrier phase and fine level at the generator or delay
line for a null at burst as shown in Figure 3-7.