Zero reference pulse: Difference between revisions

Revision as of 11:43, 17 June 2010

Revision as of 10:05, 20 June 2010

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== Modulation ==

In analogue broadcasting the composite video signal modulates the carrier by a type of [[amplitude modulation]] named [[Single-sideband modulation#vestigal sideband (VSB)|VSB]]. The polarity of the modulation is negative, i.e., higher the level of the CVS, lower the level of the RF signal. If the level of CVS is 0 volt the level of the RF signal is % 100. The [[amplitude modulation#modulationModulation index|modulation index]] is so arranged that, the maximum level of CVS yields a RF level of % 10 (sometimes % 12.5). <ref>Bernard Grob - Charles E.Herndon:''Basic Television and Video systems'', Glencoe-McGraw Hill,ISBN0-02-800437-X, p.411-412</ref> This value is known as the level of the [[residual carrier]]. If the modulation index yields more than % 10 for maximum level input (high residual carrier), the efficiency of the transmission drops, i.e., low contrast. On the other hand, if the RF level is below % 10 (low residual carrier), aural and visual signals begin to interfere each other.

So it is important to keep %10 for 1000 mV input.