What Is a Cable Amplifier?

The high frequency radio band, also called the shortwave band, begins just above the standard AM band and extends to 30MHz. It contains numerous services, including international broadcasts, amateur radio, aviation, military, and much more. Antenna cable amplifiers assist in receiving weak signals from distant stations. Because they're limited to a narrow band of frequencies -- unlike wide band amplifiers for television cable -- they can provide a much higher gain of 16db. That amounts to a 40X increase in power.

Television antenna pre-amplifiers look much like a cable amplifier, and they have the same coaxial cable connections. However, these amplifiers are designed for fringe area reception of the VHF and UHF television bands. They have very high gain, 23db in one instance, and that represents a power gain of 200 times the input.

Cable distribution amplifiers are intended for boosting signals over a wide range of frequencies, typically from 5MHz to 1000MHz. As a result, their gain is typically low, only about 4db, or about two and a half times the input power. This isn't a problem since the usual signal from a cable television provider is strong. Distribution amplifiers are used to offset losses when multiple television receivers are connected to the same cable input.

The advantage of a bidirectional amplifier over a unidirectional amplifier is that the former is capable of both receiving and transmitting. The main use for this would be in a home television cable system where televisions and computers share the connection. Like the unidirectional systems, these amplifiers have only modest gain, but since cable television signal levels are generally strong, the amplifiers are needed only to offset losses from multiple connections. The input frequency ranges from 5MHz up to 1000MHz, and the output frequency is limited to 40MHz.

Follow the manufacturer's instructions when installing a cable amplifier. Many home television cable systems have a radio frequency splitter that is often inconveniently located in a garage or attic where no power source is nearby. Some cable amplifiers can be powered remotely with a television cable providing the connection between amplifier and power supply. If a distribution amplifier has unused connections, be sure to connect a termination cap. This prevents power loss and reflections of TV signals. Never tighten the connections with a wrench. Finger-tight is all that is needed.