User talk:Gaurav6918

vestigial sideband in television transmission
== Vestigial side band  in television transmission''' ==

VSB is  a  clever  compromise  between  SSB and DSB, which  makes  it very  attractive  for  television  broadcast  systems. The baseband   video  signal  of  television  occupies  an enormous  bandwidth  of  4.5MHz, and  a  DSB  signal  needs  a bandwidth  of  9MHz  It  would  seem  desirable  to  use  SSB  to conserve  bandwidth cost. It has been stressed that the major advantage of single sideband is the bandwidth saving that accruse from it’s use, although the power saving cannot be ignored.as we seen that in dsb-sc signal ,carrier signal is also sent. We may now turn to the question of transmitting the video signals required for the proper reception of television ,note that the bandwidth occupied by such signal is atleast 4MHz.the use of some form of ssb is clearly indicated here to ensure spectrum conversation .so as simplify video demodulation in the receiver,the carrier is ,in practice,sent undiminished.Because the phase response of filters,near the near the edges of the flat band pass ,would have a harmful  effect on the received video signal in a TV receiver,a portion of unwanted sideband(lower) must also be transmitted. The result is vestigial transmission. By sending the first 1.25 MHz of the lower sideband,it is possible to make sure that the lowest frequencies in the wanted upper sideband are not distorted in phase by the vestigial sideband filter.Because only the first 1.25 MHz of the lower sideband is transmitted,3 MHz of spectrum is saved for every TV channel.since the totel bandwidth requirement of a TV channel is now 6 MHz instead of 9 MHz,clearly a great saving has been made and the channel consequently accomodated.