The cable television system in your home uses coaxial cable to distribute the signal from the outside cable system to the different televisions in your home. This coaxial cable, which is round and about the diameter of a pen or pencil, has been custom-installed, and the various links or segments of cable is connected together using "F" connectors. These round "F" connectors are installed on each end of each segment of coaxial cable by hand. The coaxial cable ends must be stripped back and cut to exact measurements to ensure that the "F" connector will make a good connection. You television is your test equipment that will tell you if the cable TV connections are performing correctly.
When you have no picture on your television set, a bad cable TV connection is a possible cause. It is not the only possible cause, so you must do a little troubleshooting to narrow down the source of the no-picture problem. The first thing to do is to determine if you have no picture on a single channel or on all of the channels. Simply click through the channels to immediately verify if they are working or not. If the other channels are working OK, it is most likely that the single channel is off due to the cable provider and not due to any problem in your house.
The next thing to do is to check the other televisions hooked up to cable TV in your home. If they all have no picture on the same single bad channel, call your cable TV provider. If all channels are off (no picture) on all TVs, the problem is most likely outside your home, and you need to call the cable TV company for service. If the other televisions are working OK and you have no picture on all channels on only a single television, a likely source of the problem is a cut cable or bad cable connection on the cable outlet connected to the television. You can visually check the cable and connectors to find out what happened to the signal. If it was working just fine earlier, most likely you will find that your dog chewed the cable in half, somebody tripped on a piece of coaxial which pulled loose from a connector or some other physical problem with the outlet. A bad "F" connector can cause no picture or a loss of signal, but this problem is usually a gradual loss of signal, over time, and is not usually an issue of something that was working well yesterday is not working today.
There are a number of things that can cause the picture on your television to intermittently flash on and off. Again, just like with no picture, you want to check all the televisions in your home to see if this problem is common to all televisions or all cable outlets. If it is common, the source of the problem is probably originating from the cable box outside your home; it could be an aerial drop wire coming into your home which can cause the signal to drop out as the wind blows up back and forth. If it is an "F" connector problem, it probably affects only one television set. On the outlet serving the television set which has the problem, one of the F connectors may simply be loose or not screwed in tightly. Another "F" connector problem which could cause a flashing picture would be in F connector where the coaxial center conductor has been cut too short and is not making good contact even though the F connector itself is secured very tightly.
A snowy picture can be the result of a bad cable TV connector or "F" connector. Again, you must check all of the television sets in your home to determine if this problem is only on one cable outlet or common to the entire house. A loose "F" connector can cause a snowy picture and simply tightening it up can correct the problem. An "F" connector which was poorly prepared with a short center conductor may be causing a snowy picture because the center conductor is not properly seated. Snowy-picture problems are not isolated to only cable TV connectors that can also be the result of damage to the coaxial cable or excessive lengths of coaxial cable serving the television which has snowy pictures. If there is excessive coaxial cable, most likely there were snowy pictures on this outlet since it was installed.
Bars and Ghosts
Bars and ghosts is a visual problem in the picture which is a result of ingress into the cable system. In extreme cases, you will see a vertical bar and multiple images as a result of outside interference leaking into the cable system. It can leak into the cable system through a damaged coaxial cable or most likely through a loose "F" connector. This is a rare problem, since DTV was introduced but it still can happen under certain conditions.