4-2
4.3
MEASURING SIGNAL LEVELS
Measure signal levels in the Level, Tilt, and Scan Modes. In Level
and Scan the process measures the difference between Video and
Audio for a channel and displays the difference in dB. In Tilt Mode,
the difference, or Tilt, refers to the difference in dB between the
upper and lower pilot channels. In terms of SAM 4040D setup,
measurement configuration parameters for Level, Frequency, and
Tilt interact, and are important factors in all three measurements.
4.3.1 Level Measurements
With Level mode selected, you can tune by channel or frequency.
Tune by
When you press Chan, the channel number and label
Channel:
appear at the top of the display (Figure 4-1). Use the
left and right arrow keys to decrement and increment
the channel number. You can also enter the channel
number by using the numeric keys, followed by Chan.
If you were in
Frequency
, Chan tunes to the nearest
channel in the channel plan
Frequency:
To tune by frequency, use the numeric keys to enter a
frequency, followed by Freq. See Figure 4-2. Use the
left and right arrow keys to decrement and increment
the frequency. The step size for these frequency
changes is programmed during setup: NAV (
Config,
Measurement
, frequency Tuning Step Size).
If you were tuning by channel,
Frequency
tunes to the
video frequency of the current channel or to the center
frequency of a digital channel. (For digital channels
setup in the channel plan, the measurement algorithm
used is for scrambled channels.)
In Level, Chan mode, you can measure the difference in video and
audio Level (dBmV) for a specific channel, expressed as dB. If one
of the readings is off-scale (low or high), use the up/down arrow keys
to see both readings on the screen. Use the left/right arrow keys to
scroll through the channels one-at-a-time.