AP01-HD_rev.09_UK
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7.3.3.
NM (Noise Margin)
The Noise Margin is a calculated estimate (in dB) of how much the carrier/noise ratio may
get worse before the reception is compromised, according to the set reception parameters
and measured MER.
The higher the Noise Margin is, the lower the chance to have troubles is.
7.3.4.
RU
The last parameter, RU, gives an idea of the signal goodness during long periods. Some
losses of signal “blocks”, in particular, may occur over the time; they appear on the TV, for
instance, as mosaics of em-spaces that overlap the picture.
RU (Reed Solomon Uncorrected – detected errors not corrected) is a register which
increases just on these cases. The worse the BER will be, the faster the RU will increase, of
course.
This register value rises from 0 to 65535 and stops at the maximum value. It is reset
whenever there is a loss of signal lock, a new tuning or a variation in the attenuator
position.
7.3.5.
CSI (Channel Status Information)
The CSI (Channel Status Information) indicates the amount of jamming signals (noise,
interferences, etc.) regarding the considered OFDM signal.
This measure is expressed as a percentage: the less reliable the reception of digital signal
is, the higher the CSI is. Thus the optimal theoretical value is 0%, the worse is 100%.
7.3.6.
USE OF MODULE
Set frequency as for a normal analogue channel. Even though measurement can be carried
out also on Measurement mode, it may be useful to visually check the presence of digital
signal positioning the instrument on Spectrum Analyzer mode.
To activate the OFDM module, press the
DIGI
key.
The indication of PWR index must be "OK" so that the module works correctly. If it is
necessary, use the attenuator. Use the lowest possible attenuation compatibly with "OK"
indication.
To change CHBW (bandwidth) and SPECTR (polarity of spectrum) press the
MENU
key,
select PARAMETERS and then press
ENTER
. The cursor appears next to “CHBW” item;
press
ENTER
,
set the desired value through the shaft encoder and confirm it pressing
ENTER
. The parameters CARR (number of carriers), MOD (constellation), GUARD (guard
interval) are automatically identified.
⇒
Remember that setting the bandwidth CHBW is very important to make the module work
correctly. Set values should generally be 8 MHz in UHF and 7 MHz in VHF.
While the OFDM module is on, you can change the tuning frequency as for UHF band in
analogue, but you shall take into consideration that the response time of the instrument is
longer, when it is on digital mode. In case of program storage, settings of digital
parameters will be stored, too, together with the other usual values such as frequency, etc.
pressing keys
2nd
+
STORE
.
To exit the OFDM function, press
SPECT
.
