AP P E N D IX D
C AR R IE R N O IS E M E AS U R E M E N T (C /N ) -AN ALO G U E C H AN N E LS -
The carrier-to-noise ratio is a measurement of the signal quality. The power of
the noise measured changes according to the resolution filter utilized. However, in
TV it is usual to refer the noise level to a bandwidth of 5 MHz. If the measurement
is reduced to a different bandwidth, the user must apply a simple correction. The
P R O M AX -6
takes the measurements in a noise bandwidth of 5 MHz.
C/N = C
L
- N
L
(dB)
N
L
: depends on the measurement bandwidth
N
L
= N
measured L
+ 10 log (BWx / BW
measured
)
There is some standards that determine the minimum C /N value in an
installation. In general greater values than 40 dB are considered good quality
signals. Lower than 40 dB you can see "snow" or graininess at the display.
