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Archives
 July 1999 Issue
Training
Evaluating Multiple Outlet Requirements,
Part 4
This months installment concludes a series on evaluating the requirements for multiple outlets. The material is adapted from a lesson in NCTIs Installer Course. © NCTI.
The previous installments in this series (Part 1, Part 2, Part 3) provided approximate worst-case signal loss values for two-, three-, four- and eight-way splitters that can be used to easily make rough estimates in the field, and combining splitters to customize the number of output ports. This installment provides information on using auxiliary house amplifiers.
An auxiliary house amplifier increases the level of a broadband signal to overcome losses from long drop cable runs and/or passive devices (e.g., splitters) that attenuate (reduce) the signal level.
Identifying house amplifier characteristics
Auxiliary house amplifiers are differentiated by: 1) the amount of signal gain or amplification (expressed in dB), 2) the number of available output ports and
3) the type of input power required (AC or DC). House amplifier gains typically range between 10 dB and 20 dB, with 10 dB gain as the most common. A single-output house amplifier is usually connected by a short coaxial jumper to the input port of a separate external splitter. A multiple-output house amplifier has an internal splitter (four-way typically) built into the amplifier housing, eliminating the need for a separate splitter.
Powering methods for house amps
House amplifiers are active devices, because they require a power source to function. A house amplifier receives its operating power either: 1) directly using a standard three-prong plug or 2) from an AC transformer plugged into an AC outlet indirectly through coaxial cable connected to a power inserter and DC transformer. The latter configuration permits mounting the amplifier outside away from any AC source in the premises security box.
Ensuring correct RF input levels
When possible, it is recommended that the input signal level be equal to or greater than the amplifiers rated noise figure (expressed in dB). Input signal levels below the rated noise figure to the amplifier may cause the TV pictures to appear grainy even though the amplifier increases the signal to adequate levels at the cable outlet. Excessively high input signal levels to the amplifier cause distortions to appear in TV pictures. - TB
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