CBNT key terms

A broadband architecture that carries signals over fiber from the headend to neighborhood nodes, then over coaxial cable to homes. Fiber handles long distances while coax serves the last segment.

The central facility where video, data, and voice signals are received, processed, combined, and transmitted into the distribution network. It houses modulators, CMTS equipment, and signal monitoring systems.

The point in an HFC network where optical signals are converted to RF electrical signals for coaxial distribution. A single node typically serves a few hundred homes.

Cable Modem Termination System. Headend equipment that exchanges data with customer cable modems, managing upstream and downstream channels for high-speed internet service.

The direction of signal flow from the headend or node toward the subscriber. Downstream frequencies typically occupy the higher portion of the coaxial spectrum.

The direction of signal flow from the subscriber back toward the node and headend. Upstream signals use lower frequencies and are more susceptible to ingress noise.

The signal route carrying services from the headend out to customers, including amplifiers and passive devices configured to pass downstream frequencies.

The signal route carrying upstream traffic from subscribers back to the headend. It requires careful alignment and noise control because many homes share it.

An active device that boosts RF signal level to overcome losses in cable and passive components. Trunk and line extender amplifiers keep levels within design limits along the plant.

A series of amplifiers connected in sequence along a feeder line. Each added stage increases distortion and noise, so cascades are kept as short as practical.

A cable with a center conductor, dielectric insulator, metallic shield, and outer jacket. It confines RF energy and delivers broadband signals from the plant to customer premises.

The inner metallic wire of coaxial cable that carries the RF signal. It may be solid copper-clad steel or stranded, and its condition affects loss and impedance.

The insulating material between the center conductor and shield of coaxial cable. It maintains conductor spacing and affects the cable's impedance and velocity of propagation.

The metallic layer of coaxial cable that contains the signal and blocks outside interference. Braid and foil combinations provide varying degrees of shielding effectiveness.

A threaded connector commonly used to terminate coaxial cable at customer premises. Proper installation requires correct strip length, a snug center conductor, and a secure shield contact.

A connector attached to coaxial cable by crimping with a compression tool rather than a hex crimper. It provides a more consistent, weather-resistant mechanical and electrical connection.

A thin strand of glass that guides light for signal transmission. Fiber offers very high bandwidth and low loss over long distances in the HFC backbone.

A permanent joint made by melting two optical fiber ends together with an electric arc. It produces low loss and is preferred for long-term fiber connections.

The reduction in light power along a fiber link, measured in decibels. It comes from fiber attenuation, splices, connectors, and splitters and must stay within budget.

A test instrument that measures received light power in fiber, usually in dBm. Technicians use it to verify that optical levels at a node or receiver fall within specification.

A device at the node or headend that converts incoming light signals back into RF electrical signals. Its input level must be correct for clean signal recovery.

The strength of an RF signal at a given point, usually expressed in dBmV for coaxial plant. Correct levels at taps and outlets keep customer devices operating properly.

A unit expressing signal voltage relative to one millivolt across a 75-ohm system. Cable technicians commonly use it to record downstream and upstream RF levels.

A logarithmic unit for comparing power or voltage ratios. In broadband work it describes gain, loss, and relative level changes along the signal path.

The loss of signal strength as it travels through cable, splitters, and connectors. Higher frequencies generally attenuate more over the same length of coaxial cable.

The difference in signal level between the highest and lowest frequencies at a test point. Proper tilt ensures all channels arrive at usable levels at the customer outlet.

A field instrument that measures RF level, tilt, and often modulation quality. Technicians use it to align plant, troubleshoot outlets, and document readings.

An instrument that displays signal amplitude across a range of frequencies. It helps identify ingress, interference, and the overall condition of the RF spectrum.

A device or circuit that compensates for cable tilt by attenuating lower frequencies more than higher ones. It keeps channel levels balanced along the plant.

The ratio of desired signal power to noise power at a measurement point, expressed in decibels. Higher SNR means cleaner signal and fewer errors.

A measure of how far a digital signal's constellation points deviate from ideal positions, in decibels. Higher MER indicates better signal quality and margin.

The fraction of transmitted bits received incorrectly. It rises as SNR or MER falls and directly affects data service reliability.

Unwanted external signals entering the cable network through loose connectors, damaged cable, or poor shielding. It degrades upstream performance and can disrupt service.

RF signal escaping from a cable system through damaged or poorly shielded components. It can interfere with licensed spectrum and indicates plant defects that need repair.

A field instrument, often used in a vehicle, that finds escaping RF energy by tuning to a known carrier. It helps locate faults and satisfy leakage monitoring requirements.

A safety procedure that isolates energy sources and applies locks and tags before work begins. It prevents accidental startup or release of hazardous energy during maintenance.

Gear such as gloves, safety glasses, hard hats, and high-visibility clothing worn to reduce injury risk. Appropriate PPE is required for tasks like climbing, splicing, and handling cable.

Connecting cable plant and equipment to earth to safely dissipate current and reduce hazards. Proper bonding and grounding protect people and equipment from electrical surges.

Electrically joining metallic components so they remain at the same potential. Bonding prevents voltage differences that can damage equipment or create shock hazards.