Measuring The Power Of Digital Channels - Promax MC-577 Manual De Instrucciones

USER'S MANUAL MC-577.

4.2.6.2 Measuring the power of digital channels

The main characteristic of digital signals is that they distribute their energy across
the entire channel bandwidth (in the same way as a noise signal), in other words they
do not posses a differentiated carrier. Given this different nature from analogue signals
the method used for measuring can not be the same. You must use a detector
appropriate for signals of a 'noisy nature' and take into consideration that the bandwidth
of the measuring filter is smaller than the bandwidth of the channel.
The MC-577 takes into account the properties of digital signals and enables the power
of digital signals to be measured almost automatically, just follow the procedure below:
Select the Spectrum Analyser operating mode, SPAN mode, and with the help of
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the frequency counter display [23] tune the signal using the TUNING [25] and FINE
TUNING controls [27]. Adjust the SPAN control [24] to select a bandwidth so that
the signal occupies the most part of the image.
Select the digital signal measurement scale CH POWER [33], the DIG key [11]
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should be in the pressed position and the DIGITAL indicator [31] should remain lit.
- Read the level on the screen with the help of the scale calibrated in dBµV
(25-75 dBµV) CH POWER [33]. If the level is very close to 75 dBµV or is greater
than this value, the signal should be attenuated using the RF attenuators.
- The actual signal level is calculated in the following manner:
Power [dBµV] = Measurement [dBµV] + Atten. [dB] + Correction Factor [dB]
THE CORRECTION FACTOR IS OBTAINED FROM THE CORRECTION CHART
WHICH IS DELIVERED WITH THE INSTRUMENT. THIS VALUE DEPENDS ON THE
FREQUENCY.
EXAMPLE B.- Measuring the power of a digital signal
Take the following figure as an example, showing a digital signal:
05/2003
VERY IMPORTANT
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