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NOTE: If the C/N measurement value is outside the specified range,

the numerical result will change from black to gray.

To edit the bandwidth, press the BW soft key. The bandwidth can

be adjusted by using the UP and DOWN arrow keys or by entering a

value using the numeric keypad and then pressing the ENTER key.

The FCC specification for C/N measurements is a bandwidth of

4.200 MHz. CATV organizations outside of the United States may

have different requirements. Measurement BW can also be defined

individually for each channel in the Channel Plan setup menu.

Noise Offset Frequency Adjustments

The frequency at which the noise level is measured is the Carrier

frequency plus the noise offset. To adjust the noise offset, press the

OFFSET soft key. The offset can be adjusted by using the UP and

DOWN arrow keys or by entering a value using the numeric keypad

and then pressing the ENTER key. Noise Offset values can also be

defined individually for each channel in the Channel Plan setup

menu.

Note: BW and Noise Offset values can be defined individually for

each channel (see section 4.3.4 "How To Edit Channel Parameters").

When tuning by channel number, the BW and Noise Offset values

are obtained from the channel plan. After tuning to a channel, the

values can be adjusted using the Offset and BW soft keys. However,

these adjustments will affect the C/N screen only and will not change

the setup values in the channel plan.

4.8 HOW TO MEASURE HUM

Hum is undesirable modulation of the television video carrier by

power line frequencies and harmonics (e.g., 60 or 120 Hz), or other

low frequency disturbances (FCC limit: < 3%). To measure Hum,

simply press the Hum key when tuned to any non-scrambled chan-

nel. In the Hum mode the hum modulation of the tuned channel or

frequency will be displayed in either % or dB as selected by the

operator. The units setting selected in the Hum screen (% or dB) will

determine which units will be used to measure Hum during subse-

quent Auto Tests. Be sure to set the desired units in the Hum screen

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