Analogue Tv: Measuring The Video / Audio Ratio (V/A) - Promax TV EXPLORER HD Manual De Usuario

LEVEL: Level indication on the upper part of the screen (analogue
bar).
C/N: Carrier/Noise ratio measurement.
V/A: Video/Audio ratio measurement.
FM Deviation: Measure the frequency peak deviation for any modulated
analogue carrier in FM.
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.

5.13.2 Analogue TV: Measuring the Video / Audio ratio (V/A)

In the Audio/Video measurement mode, on the screen appears the following
information:
Figure 18.- Measurement of the video/audio ratio.
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USER'S MANUAL. TV EXPLORER HD
WARNING
11/2009