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NOT 562-2002-en

GHOSTING.- HOW TO FIND THE ORIGIN

Description: 

ghosts that appear to the left of the picture are (and assuming that they are not present in the headend) are due to ingress of the signal into the distrubution network.

on the other hand those ghosts that appear to the right of the picture are generally produced by impedance mismatching as it happens when distribution elements featuring poor return losses are used.

being:

  1. w: the horizontal width of the tv set screen
  2. d: the displacement of the ghost in the screen
  3. vp :velocity of signal propagation for the cable
  4. 25845 a constant derived from the speed of light multiply by the scan time for horizontal line.
  5. l:the distance between the source of the reflection and the re-reflection.

lcan be evaluate with the following formula:

l= (d/w)*vp*25845 feet

example:

let us assume

  • w=28 inches,
  • d=0.15 inches,
  • vp=0.85

then

d= (0.15/28)*0.85*25845= 117.69 feet

between both devices.

the next step is check the layout of the network to find where there are devicesl feet apart and that this distance is between the source of the signal and the tv set.

Id Anrterior: 
87
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