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4.5 HOW TO MEASURE TILT - BALANCING AN AMPLIFIER
A cable system is designed for unity gain, and the output of each like
type of amplifier (trunk, bridger/line extender) output should be as
close to identical as physically possible. The amplifiers are set up
with specified levels for signals at the high and low end of the
spectrum that are used for Automatic Gain Control (AGC) or Auto-
matic Slope Control (ASC). In the amplifier balancing process, these
signals are measured and adjusted to specification. Before making an
adjustment, ensure that there are no problems in the system that
should not be compensated with an adjustment but repaired instead.
To balance the amplifier, ensure that the AGC and ASC is switched
off. Tilt mode simplifies the actual balancing by displaying a bar
graph with a representation of up to nine different user selected
video carrier levels. Adjust the high pilot level to the specified level
using the gain control. The gain control tends to affect the overall
amplitude throughout the spectrum equally. Adjust the low pilot
level to the specified level using the slope control. The slope control
affects the low end of the spectrum more than the high end. Due to
the interaction between the two controls, repeat this process until the
pilots are "balanced". Then switch on the AGC and ASC, wait a
moment to measure the signal levels with the AGC and ASC acti-
vated.