4.2.4.2.1 F 3 function: F requency shift for the C /N measurements
To select the frequency shift in the C/N measurement, press the F C T [13] key,
then use the rotary encoder to select the F 3 function and press the F C T key [13]
again. Turn the rotary encoder until the desired shift is displayed. Lastly, press the
F C T
[13] key again to select the shift.
This parameter is defined at factory as 4.5 M H z ; this shift allows to make C/N
measurements directly when there is no adjacent channel at the lower frequencies.
4.2.4.2.2 M easuring the C /N ratio with no adjacent channels present.
To perform this measurement, proceed as follows:
1) Select the digital channel measurement mode.
2) Tune the main carrier of the channel and wait a few moments until the reading
level stabilises.
3) Select the frequency shift of the noise level measurement by means of the F 3
function to 4.5 M H z with respect to the main carrier. 4.5 MHz is the value
predetermined at factory for this parameter, so if it has not been modified
through the F3 function it will not be necessary to redefine it now.
4) Press the C /N [14] key.
5) Wait until the reading stabilises (10 seconds maximum).
When the C /N [14] key is pressed, the equipment performs a series of
automatic measurements so as to come as close as possible to the real value of
the noise level. The time this takes depends on the content of the image that is
being transmitted and the C/N value itself.
When the noise level is lower than the equipment's sensitivity, a limit value ">"
is displayed to indicate that the C/N value to be measured is greater than this limit
value.
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