What Is a Distribution Amplifier and Do I Need One?

The goal and purpose of a distribution amplifier is to increase the strength of received signals to a level that is greater than the signal losses associated with the distribution system. To ensure all your devices receive proper strength signals, it’s important that your distribution amplifier be centrally located (relative to distribution lines), since the longer the lines, the more signal loss there will be within the system.

Channel Master has engineered and produced superior quality TV signal distribution amplifiers which offer professional grade performance that support both analog and digital broadcast signals. Channel Master offers this amplifier with one-way (1-Port), two-way (2-Port), four-way (4-Port), and eight-way (8-Port) distribution ports which have the lowest distortion performance available. In addition, Channel Master distribution amplifiers have precision machined SCTE conforming sealed "F" ports and have a cast aluminum housing, powder coating, and are weather sealed for corrosion resistance.

Channel Master TV signal distribution amplifiers are typically mounted indoors, but are safe to use outdoors as well. They are designed to distribute signals to multiple outlets within a house, or when there are very long coaxial cable runs to TV outlets. In areas of very weak signals with an off air antenna, you may need to use a preamplifier at the antenna first to increase the signal levels to a attributable level.

Number of output ports

Channel Master TV signal distribution amplifiers are manufactured with one (1-way), two (2-way), four (4-way), and eight (8-way) output ports. All output ports of a single amplifier will have the same strength signal available, but the actual signal boost (gain) is determined by the number of outputs on the amplifier. The reason for this is that the amplifier has a fixed amount of gain, and as the output signal is divided to more ports, there is less signal available for each port. For instance, with a 1-way amplifier, 100% of the gain of the amplifier is available at the output port. With a 2-way amplifier, only 50% of the gain of the amplifier will be available at each output port. For a 4-way amplifier, the signal is divided four ways, so there is only 25% of the signal available at each output port. For an 8-way amplifier, there is 12.5% of the signal available at each output port. Graphically, it looks like this:

 Amp_Splitter1.jpg

This situation will be the same whether the amplifier has multiple outputs, or only has one output and an external splitter is attached to that output.

Return Path Capability
In a cable telecommunications network, cable modems, Multimedia Terminal Adapters for cable telephony (MTAs), and set top boxes will all need to be able to transmit signals back into the cable network to allow for two-way communications. To do this, signals are sent back into the cable network in the 5 to 42 MHz range. This is called the return path. Channel Master distribution amplifiers all have the ability to pass signals in the return path back to the cable network.  This has no impact on the performance of the distribution amplifiers when they are used with TV antennas since that frequency range is not used for off-air TV reception.

Amplifier Gain

Amplifier gain is the amount the distribution amplifier will boost the TV signals. This is usually given in dB. Positive dB is signal gain, and negative dB is signal loss. In most distribution amplifiers, there is a fixed 15 dB of gain. However, the internal splitters that provide multiple outputs add signal loss, or negative dB. In a two output distribution amplifier, the signal splitter on the output of the amplifier will divide the signal into two separate output ports. Each output port will have approximately 50% of the signal level coming out of the amplifier. Splitting the signal into two output ports with 50% of the signal on each port will cause the signal level to drop by approximately 3.5 dB. A four port amplifier will have 25% of the power on each output port, which is approximately 7.5 dB of signal loss due to the splitter on the output. If a distribution amplifier has 15 dB of fixed gain, a four output distribution amplifier will have an effective gain of about 7.5 dB per port (15 dB gain – 7.5 dB splitter loss) from the input port to the output port(s).

Power Inserter

A power inserter is used to back feed power to the distribution amplifier through one of the RF output ports so the distribution amplifier can be mounted at a location where power is not available. In most installations, it will not be necessary to use the power inserter since the amplifier is usually mounted near a power outlet. There are no performance advantages to using the power inserter – it is only used to allow the unit to be remotely powered when the amp can’t be located near a power outlet.  Channel Master distribution amplifiers do not include a power inserter with them, but they are available from other sources if one is needed.

Using Distribution Amplifiers

For many antenna installations, a preamplifier at the antenna may be all the amplification needed.  The Consumer Electronics Association (CEA) has created a color code rating system for antennas, and has developed a web site, www.antennaweb.org, to assist the homeowner in determining the optimum antenna for their location.  For homes in the Red, Blue, and Purple zone channels, it is preferred to use a preamplifier at the antenna instead of a distribution, or drop, amplifier in the house.  If the number of outlets is low and the cable lengths are short, this may be all the amplification that is needed.  In installations with long cable runs and multiple outlets, it may be necessary to use both a preamplifier at the antenna and a distribution amplifier inside the house.   The preamplifier will ensure that the distribution amplifier is receiving sufficient signal levels.  If the signal levels are already bad at the input to the distribution amplifier, they will not be improved by amplifying them.  On the other hand, distribution amplifiers are not designed for very high level input signals.  Using a preamplifier on an antenna in areas with strong off air signal levels, or using a preamplifier with high gain and a short cable run from the preamplifier to the distribution amplifier, can easily result in overdriving the input of the distribution amplifier. 

In Yellow, Green, Light Green, and some Red zones, signal levels are usually strong enough at the antenna that a preamplifier is not required.  However, for multiple outlet installations, a distribution amplifier is recommended to ensure that signal levels to each outlet are maintained at high enough levels to prevent drop out of the TV signals.

The best way to determine if a distribution amplifier is needed is to measure the received signal levels with a field strength meter, both at the input to the first splitter and at each outlet in the home.  Since this is not usually available for most home installations, determining if an amplifier is needed can be a challenge.  As a rule of thumb, when trying to view TV stations in the Red, Blue, and Purple color code areas, a preamplifier should always be used.  If there are four or fewer outlets in the home and the cable length from the antenna to the furthest TV set is less than 75 feet, a distribution amplifier will probably not be needed in most cases.  Distribution amplifiers are easy to add, so it is recommended that the installation be done without the distribution amplifier first, and then only add it if needed after the installation is complete. 

If there are more than four outlets, and/or the cable length from the antenna to the distribution amplifier input is 50 feet or longer, and the cable length from the distribution amplifier to the TV set are 25 feet or longer, a distribution amplifier will probably be needed.  (Please see the document titled “Do I need a preamplifier for my antenna?” for information on selecting the correct preamplifier.)

The recommend way to use a distribution amplifier is for it to be centrally located, and for it to be the first device on the coaxial cable coming from the antenna/preamplifier (if used) after the ground block.  It is always best if all the outlets in the home are individually wired back to the distribution amplifier location.  If three or four outlets are in the home, a four output distribution amplifier should be used.  If five through eight outlets are in the home, an eight output distribution amplifier should be used.  Any unused ports should be terminated.  If more than eight outputs are needed, a more detailed design will be needed to ensure the correct signal levels to each outlet.  Please contact Channel Master Technical Support at techsupport@channelmaster.com for assistance.

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