Does anyone know what causes 'ghosting' of a TV picture?

 

A poor signal.

 

A reflected signal.

 

As Joed said, ghosting is caused when a direct signal and a reflected signal reach your antenna at the same time. Repositioning the antenna is your best solution.

 

Your antenna gets one signal, then that same single may reflect off a building back to your antenna with a time delay.
Your TV shows more then one picture signal with that delay as a ghost.
Multi-images of the same picture shifted by time delay.

 

There are 2 general causes for ghosting in TV signals over the air.

The most common cause is 2 or more different paths for the signal to follow. You get the straight direct signal, plus you get a signal that bounces off something like a building at some lateral direction. The path to the building then to you is longer so every part of the picture is replicated with some shift to the right. This is called "multipathing". A larger more directional antenna helps eliminate multipathing by getting a stronger direct signal and a weaker indirect signal.

A less common, or less severe, cause involves poorly designed, mismatched, or improperly installed filters. These filters cause multiple ghosts due to an effect called "ringing". It gets that name because the same effect, if heard in the audio spectrum, would sound like the ringing of some resonant piece of metal or stiff material. A related effect that can look similar is called "group delay". Cable TV filters intended to notch out premium channels tend to be cheap and add these problems. A cheap analog tuner in an old TV can also be a cause.

 

You don't really provide much information into your situation, but if you have CATV and the ghosting is limited to certain channels between 2 and 13, the most common cause of this is a strong broadcast signal that coax picks up like an antenna. If the ghosting is worse on upstairs TV's this is probably the cause. Placing a ferrite bead over the coax near the set, should help reduce the problem. Making sure you coax has the connectors installed correctly and the shield is properly grounded should help some too.

 

FWIW I had ghosting on two or three channels with my cable connection. Started out not bad and got worse over time. Finally (they were channels I didn't usually watch) called a had a tech come out.

He said the coax was corroded - the copper core was black - and cut off a couple of inches and put on a new F connector both inside and at the pole the line comes off of. Ghosting gone.

Don't know if this is helpful but thought I'd pass it along ...