text: i wanted to know how does earth effect on parameters of a transmision line? i have power systems course and we should find the answer to this question but i can't find any good answer the transmission line should consist of the core conductor and the shield.  the shield should be tied to earth (ground) at the source end, which will shunt unwanted (spurious) signals to ground.  this prevents them from being induced onto the transmission line and causing weak/distorted signals at the termination.  i hope that helps.  p.s. -  never tie both ends of the shield to earth...it causes an earth loop which shows up as a ghost image of the original transmission that is out of phase (sync) with the original.