Why do we keep losing our picture and a no signal message pops up my tv screen?
One of the biggest problems in tv reception is additional offending signals from other sources. In the old analog reception, these problems would show up as snow, lines or ghosting in the picture. With digital tv, these same problems cause the complete loss of signal.
The sources of interference are many and always a challenge as they are not necessarily constant, due to the way a radio signal propogates.
The two main problems that any tv reception facility experiences are co channel and mutipath interference.
Co channel is an undesired tv station from far away that is on the same frequency as the desired channel.
Under certain atmospheric conditions, that signal can carry very long distances. Because it is on the same frequency as the desired channel, the receiver can not differentiate between the two and locks up and generates the no signal message. This ususally occurs during the hazy summer days. In the old analog medium, we would actually receive tv stations from as far away as Florida!
What we seem to be experiencing lately is caused by multipath distortions or reflections. These reflections can be caused by a building, mountaintop, airplane, or in our recent case, I believe, the leaves are starting to bud and creating reflections. Hopefully, it will settle down soon.
A pretty good article on mutipath signal problems can be located here:
http://kh6htv.com/application-notes/tv-propagation-multi-path-effects/
Lots of atmospheric problems this week, predominatly on Monday. Looks like it has settled down some. I actually picked up a tv sation from Baltimore, Maryland, which was wiping out channel 21. Oh for the old analog days.
ReplyDelete