An RG-59 cable is made of four components. The outer plastic sheath provides outer protection. Underneath that is a copper-braided shield, to provide further protection. An inner dielectric insulator insulates the cable. The final piece is the copper-plated core, which lies underneath all of the other components.
The cable operates at a characteristic impedance of 75 ohms. The cable is typically used for baseband frequencies. Baseband frequencies are signals whose frequencies start at zero. Composite video, a popular signal used in televisions, is a baseband frequency. The RG-59 can also transmit high frequencies, such as broadcast frequencies, although not as well.
RG-59 cables are only effect at short distances. Over longer distances, they have a high-frequency power loss that makes them makes them less than an ideal choice for transmitting high frequencies. They are effective at short distances, which is why they are commonly used for connecting devices within 5 or 6 feet.
RG-59 cables are frequently packaged with devices such as VCRs and cable boxes, due to the fact that they are more effective at short ranges. Since these devices are usually within a couple of feet of the television they are connected to, RG-59 cables are the ideal choice to transmit the composite video signal.
Where RG-59 cables are ineffective at long ranges, RG-6 and RG-11 cable take over. These cables are similar in design and function, but they do not have the high frequency power loss that the RG-59 does and are more useful for doing the same job at longer distances. Fiber-optic cables are even more effective, and many cable companies have begun the switch to implementing fiber optics into their cable networks.