USER’S MANUAL. PRODIG-5
11/2006 Page 47
English
WARNING
When at the RF input appear an important number of carriers with a high level the
tuning circuit may become out of control, giving as a result wrong level measurements.
To be able to determinate the equivalent level of a carrier group (with similar levels) at
the RF input, it is possible to use the expression:
L
t
=L + 10 log N
L
t
: equivalent total level
L: average level of the carriers group
N: number of carriers
So, if there are ten carriers with a level around 90 dBµV, their equivalent level will be:
90 dBµV + 10 log 10 = 100 dBµV
Observe that in this case, loss of tuning by overload of the RF input may occur besides
other effects such as tuner saturation and generation of intermodulation products that
may mask the spectrum visualization.
5.14.2 Analogue TV: Measuring the Video / Audio ratio (V/A)
In the Audio/Video measurement mode, on the screen appears the following
information:
0 10 20 30 40
LEVEL:
C/N:
» V/A:
79.2
40.1
16.2
dBµV
dB
dB
FREQ:
CH:
168.25 MHz
S10
Figure 22.- Measurement of the video/audio rate
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