R&S FSL Cable TV Measurements (Option K20)
1300.2519.12 2.85 E-11
• A Modulation Standard is referenced. In case of an empty channel, the modulation standard is
set to < unused >. Be aware that modulation standards have to be created before making use
of them. For details refer to section Create modulation standards Note, that in order to perform
channel table based measurements, there must be at least one channel, that references a
m
odulation standard. It is not possible to do any measurements, if in all channels the
modulation standard equals < unused >.
• The RF frequency represents the characteristic frequency of a channel. For analog TV
channels RF is equal to the vision carrier frequency. For digital TV channels and < unused >
channels it equals the center frequency.
• Width stands for the channel's bandwidth.
Channel 2Channel 1 Channel 3
Analog TV< unused > Digital TV
RF 1
RF 2
RF 3
1.25 MHz
Start 1
Start 2
Start 3
Stop 3
Stop 2
Stop 1
Width 1
Width 2 Width 3
Frequency
Amplitude
Fig. 2-61 Channel start and stop frequencies versus RF frequency and channel width
Except for < unused > channels the calculation of the start and stop frequencies depends on the signal
type property (digital or analog TV) of the referenced modulation standard. All corresponding formulae
are listed in the table below.
Table 2–9: Channel start and stop frequencies versus RF frequency and channel width
Signal type Analog TV Digital TV < unused >
RF frequency
Start + 1.25 MHz Start + (Stop – Start) / 2
Channel Width
Stop – Start
Start frequency
RF – 1.25 MHz RF – Width/2
Stop frequency
Start + Width
Note: The Cable TV Measurements option automatically adapts the RF frequency if the user changes
the modulation standard of a channel (e.g. from an analog to digital modulation standard). This
is done in order to keep the channels start and stop frequencies constant.
Modulation standards
All over the world many different transmission standards for TV signals exist. As a guide through the
jungle of parameters that describe TV signals (including video and sound sub–signals) the concept of
the modulation standard has been introduced.
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