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Digital Analysis (QAM View OPT4): QAM Ingress Mode

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Measurement data is shown on two lines, A and B, below the graph. These

two lines show the readings of the vertical markers on the graph.

Press this key to select the active vertical marker. The dotted

line is the active marker. The solid line (other marker) does not

move. The active marker moves with the left and right diamond

keys.

Press this key to automatically place the active marker at the

frequency with the greatest amplitude.

Editing the Modulation Format or Symbol Rate

Press this key to edit the modulation format.

The SDA analyzes two quadrature amplitude modulation formats, 64 QAM

and 256 QAM. Changes to the modulation format should be made only

when it is certain that the modulation of the digital signal is not

compatible with the current setting.

Use the up or down diamond keys to select the alternate modulation format,

and then press the Enter key. Edits to the modulation format may be saved

to the Channel Plan.

Press this key to edit the Symbol Rate.

The Symbol Rate corresponds to the size and shape (bandwidth) of the

digital signal. This rate is expressed in “millions of symbols per second”

(Msym/s) and may be edited in the Digital Summary Mode. The default for

64 QAM is 5.057. The default for 256 QAM is 5.360.

Edits to the default rate should be made only when more accurate data is

obtained from equipment specifications or further analysis of the signal.

Use the alphanumeric keypad to define the new symbol rate, and then press

the Enter key. Edits to the symbol rate may be saved to the Channel Plan.

Press this key to select the LEVEL submenu, where the

following items may be edited:

• Reference Level

• Scale Parameter

• Maximum Hold Function.

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Wavetek 147 Specifiche Pagina 187