Figure 13
Figure 14
Figure 15
AUTOMATIC CENTER FREQUENCY DEFAULT –
NTSC DIGITAL CARRIERS
If a digital channel is being enabled in the channel plan edi-
tor, please observe that an auto center frequency feature has
been implemented for NTSC channel plans. This feature adds
1.75 MHz to the video frequency of the channel being modi-
fied, and the measurement bandwidth now defaults to 5.6
MHz. Adding 1.75 MHz to the video frequency establishes the
center frequency in a standard 6 MHz bandwidth. The user
should always verify the 5.6 MHz measurement bandwidth
with the system operator, and adjust as needed.
EXAMPLE: Channel 89 is being converted from a video chan-
nel to a digital channel. The video frequency is 613.25 MHz,
and the measurement BW is 4 MHz (Figure 16). After convert-
ing the channel to a digital carrier, the center frequency is
615.00 MHz, and the measurement bandwidth is 5.6 MHz
(Figure 17).
Figure 16
Figure 17
QAM VIEW OPTION FOR SDA LEVEL METERS
Once you have upgraded the SDA platform, you can purchase
the QAM View Option 4 to ensure the quality of your forward
digital services. For measurement and analysis of digital TV
and forward modem signals, the new digital QAM View option
provides a full complement of digital quality measurements.
Included is a 64/256 QAM constellation display with zoom
average digital power level and BER and MER (Figure 18). An
equalizer display shows equalizer stress and distance to fault.
In addition, an exclusive noise mode allows technicians to
see ingress/noise under an active digital carrier (Figure 19).
This tool is invaluable for detecting forward path ingress oth-
erwise hidden by conventional spectrum views!
Figure 18
Figure 19
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