There are three standard sizes of coaxial cable used for TV distribution systems in homes. These are Series 59, Series 6, and Series 11 (commonly called RG59, RG6, and RG11). Series 59 is the smallest, and Series 11 is the largest. Series 59 is not used very often any more due to its high signal loss over length. Series 11 is the largest, has the least amount of signal loss over length, but is bulky, hard to install, and relatively expensive when compared to Series 6 coaxial cables. Series 6 is the most commonly used size due to the excellent trade off in price, size, handling and signal loss. The following information is specific to Series 6 coaxial cable.
Signal loss through a length of coaxial cable is primarily a function of two things: Length and Frequency. The longer the length of a piece of coaxial cable, the more signal is lost. The higher the frequency of the signal passing through the coaxial cable, the higher the loss over a given length. Coaxial cable loss is normally specified in dB loss per 100 feet of cable. For Series 6 cable, typical loss values are as follows:
Channel 2 ………... 1.5 dB/100’
Channel 13 ………. 3.0 dB/100’
Channel 14 ………. 4.5 dB/100’
Channel 51 ………. 5.6 dB/100’
950 MHz …………. . 6.4 dB/100’ (bottom frequency of the satellite IF for DirecTV or Dish Network)
2150 MHz ………..... 9.7 dB/100’ (top frequency of the satellite IF for DirecTV or Dish Network)
It’s important to remember that these losses are provided for 100 foot lengths of cable. If only 50 feet of cable is used, the loss will be half of the value given above (i.e. 2.8 dB of loss at Channel 51).