The most asked question in any cable service system is the one above. There are many reasons why pictures vary from channel to channel but we will deal here with a few.
1. Off air vs. Satellite reception ("off air" means the channel is broadcast over land on a standard broadcast frequency referred to with a number from 1 to 13. )HF channels are from 14-84 and are also available in this area. (Example is Fox CH 14 Amarillo Texas). Off air channels are more likely to be interferred with due to the distance they must travel through the atmosphere and the tendency for the actual curve (ball) of the earth to shield the broadcast from the receiving antenna. Although Television signals are basically line of sight (same as light) they do bend through atmosphere much the same way light bends in water. In some cases water in the atmosphere causes bending beyond normal and humidity plays a part in how much bending occurs. This and other factors such as layers of air that have different temperatures also cause bending much the same as "Mirage". This allows for TV reception beyond the actual limits that the curve of the earth places upon propagation of signal from Transmitter to receiver. This simply means that "off air" signals are less likely to arrive as perfectly as signals from Satellite Systems due to the fact that Satellite signals only have to penetrate the heavier parts of the atmosphere 5 to 10 miles whereas off air signals have to penetrate up to 100 miles of unpredictable air conditions in order to be received. Satellite signals are also subject to air variations and may also fade during periods where air is greatly saturated with moisture. Although they travel thousands of miles from their Geostationary orbit positions it is only the last few miles where problems occur*. Often during snow or rain satellite signals too will fade.
*Satelllite signals will also fade during 2 periods (fall and spring) due to the fact that their orbit is stationary but eventually the tilting of the earth aligns them between the receiving dish on earth and the transmitting satellite for a few minutes each day when the sun is directly behind the satellite. The sun is a far more powerful tranmitter of radiation than is the satellite transmitter and thus covers up the signal with noise generated by storms and radiation occuring all the time on the sun's surface.
2. Interference from terrestial causes is another problem. Although cable systems are designed with coaxial cable (more like a wire inside a pipe) that limits by a factor or thousands the interference in the proximity of your cable wires inside your home or outside in the alley. Off air signals are susceptable to interference at their receiving antennas (towers with large antennas pointed at the source transmitter) in spite of all other preparations. Things such as electrical insulators leaking high voltage, livestock electric fences automobile ignitions, welders, medical equipment and computer systems all generate something called RFI (Radio Frequency Interference). This produces several effects to TV pictures that appear as snow, sparkles, lines of sparkles and frying sounds in audio. In General these things are unavoidable unless there is a system or TV receiver fault. They may be intermittent or constant depending on what's causing them. Sometimes they can be eliminated by Cable crews or at least located. One particular key to identification of t hem is whether or not they interfere on all channels. If Satellite signals are clear then it's a pretty good sign the local wiring and equipment is not a fault. More often it is an unavoidable or at least unfixable problem with a noise generating device such as those mentioned above.
3. In home wiring as a cause of reception problems is also a vary often occuring problem when some channels are good and some are not. Even when no interference is entering the systems a loose connector (at least finger tight) can be the cause. Connections that push on vs. those that have threads to tighten them are a very common cause. Pinched or scraped cables can loose their shielding properties and also become a ingress point that will cause interference but again this is usually common to all channels.
4. Improperly installed customer hardware is also a very common problem. Splitters and other devices may be installed with poor connections or wrong hardware. They can also be connected so that input ports are not connected correctly. This can cause loss of one or more channels, even loss of sound and color without affecting all sets connected the same. The most common error is TV receiver connected to input port and cable connected to output port. In this case one set works OK but other connected to the same splitter does not.
There are many other causes and your cable company is familiar with remedies and has the information you might require. Please contact us at any time with your questions regarding this subject or any other you would like to know about.
