Measuring The C/N Ratio Of Analogue And Digital Signals; Measuring The C/N Ratio Of Analogue Channels - Promax MC-577 Manuel D'utilisation

Figure 9.- Example of digital channel power measurement.
Using the CH POWER scale [33] (blue background) you can read a power
of 45 dBµV .
From the correction chart in figure 8, you obtain the Correction Factor to be
applied to the frequency you are working with (650.00 MHz) which is 0 dB . Therefore,
the actual power of the channel is:
Power [dBµV] = Measurement ( 45 dBµV ) + Atten. ( 0 dB ) + Correct. Factor ( 0 dB ) = 45 dBµV
To obtain further information on the digital signal measurement method refer to
Appendix A Digital TV signals .

4.2.6.3 Measuring the C/N ratio of analogue and digital signals

Measuring the Carrier/Noise ratio provides us with information on the quality of
analogue signals and the sturdiness of digital signals. The Spectrum Analyser
operating mode, SPAN mode, enables this measurement to be made almost
automatically.
To measure C/N, the MC-577 measures the maximum level or power (depending on
whether the analogue or digital measurement mode has been selected) present inside
the represented bandwidth (defined by the SPAN control [24]) and subtracts the
minimum noise level measured inside this bandwidth. Therefore, for the measurement
to be correct it is essential that the maximum and minimum level signals appearing on
the monitor are those for which you wish to evaluate the C/N ratio.

4.2.6.3.1 Measuring the C/N ratio of analogue channels

- Select the Spectrum Analyser operating mode, SPAN mode, and press the audio
control [28] so that the C/N measurement bar does not get in the way when
choosing the right SPAN .
Select the analogue signal measurement scale, LEVEL [34], the DIG key [11]
-
should be released and the ANALOG indicator [32] should remain lit.
Page 24
USER'S MANUAL MC-577.
Measurement conditions:
Central frequency:
RF attenuation:
Mode:
650.00 MHz
0 dB
DIGITAL
05/2003