Glossary of Terms

 A/B Switch – A device that allows two devices to connect to a single signal source, with only one device being connected at a time.  An A/B switch can also be used to switch between two signal sources connected to a single receiving device, connecting only one source at a time. 

Acrylic Insulator – A plastic material that is used to weatherproof outdoor antenna system connections.  It is applied in liquid form, typically by aerosol can.

Active DeviceA device that contains electronic components requiring power for it to function properly.

Active ReturnA 2-way device that has amplification in the return path.

Advanced Television Systems Committee (ATSC) – An international consortium of electronics and telecommunications companies that develops voluntary standards for digital television including the specifications for what is now known as HDTV (high definition television). 

Alignment Bearing (rotor) – A ball bearing-equipped guy ring that is slipped onto the antenna mast above the rotor to permit guying of the mast section rotated by the rotor.

AmplifierAn electronic device that increases the input signal by some amount, typically stated in dB gain.

Antenna Color Code – A system created by the Consumer Electronics Association (CEA) to assist the consumer in selecting the appropriate outdoor antenna based on a number of factors.  The color codes are as follows:

Yellow – Small multidirectional antenna for use in very strong signal strength areas

Green – Medium size multidirectional antenna for use in strong signal strength areas

Light Green – Large amplified multidirectional antenna, small amplified directional antenna, or medium directional antenna for use in areas with  moderate signal strength

Red – Medium directional antenna for use in areas with moderate signal strength and strong reflected signals that may interfere with the desired channels

Blue – Medium amplified directional antenna for use in areas with weak signal strength

Violet – Large amplified directional antenna for use in very weak signal strength areas

The CEA has created a web site, www.antennaweb.org, that provides the antenna color code information for all available TV channels based on the entry of the address where the antenna will be used.  The CEA Color Code is based on optimum conditions over unobstructed terrain. What lies between a transmitter and an antenna installation will have a direct bearing on what type of antenna is appropriate.  Factors to consider are: the power output and height of a transmitting antenna tower, the type of terrain between the tower and the receiving antenna, and the size and number of buildings that lie in the path of the transmission.

Antenna Discharge Unit (Lightning Arrestor) – A small device that is inserted into the transmission line and connected to a grounding wire or strap to discharge static electricity to ground before it can enter and damage a TV receiver.  This is usually only used on 300 ohm twinlead installations.

Array, Multiple – See Multiple Array

Aspect Ratio – The ratio of the width of an image to its height.  Common aspect ratios for TV sets are 4:3 (NTSC Standard Definition) and 16:9 (ATSC High Definition).  When it is necessary to convert the aspect ratio to fit the format of different display devices (TV, PC screen or portable device),  techniques such as zooming and cropping, letterboxing (horizontal black bars), pillarboxing (vertical black bars) and stretching are used to fill the screen of the display device that has a different aspect ratio.

Attenuation – A decrease in the strength (level) of a signal as it is transmitted or carried by wire(s) from one point to another. In antenna systems, attenuation is usually an undesirable characteristic.

AttenuatorA device used to lower signal levels by a predefined amount, typically stated as dB loss.

Automatic Gain Control (AGC) – an electronic circuit that automatically adjusts the gain of an amplifier.

Balun (matching transformer) – A small device that matches the impedance of one component, transmission line, or circuit to that of another to prevent loss of signal strength and other unwanted characteristics. In antenna systems, baluns typically are used to match 75 ohm coaxial cable to the 300 ohm output of an antenna or the 300 ohm input of an older TV. 

Band, Low (TV) – See Low Band

Band, High (TV) – See High Band

Band Rejection Filter – A circuit or device that blocks a specific frequency or channel, or group of frequencies or channels, while passing all others. 

BandpassThe range of frequencies a devices passes (see Passband and Bandwidth), normally expressed in units of Hertz (kilohertz, Megahertz, etc.).

Bandpass Filter – A circuit or device that passes a specific frequency or channel, or group of frequencies or channels, while blocking all others. 

BandwidthThe range of frequencies a device is designed to pass, or actually does pass (used interchangeably with Bandpass and Passband), normally expressed in units of Hertz (kilohertz, Megahertz, etc.).

Beamwidth – The angle formed by the two compass directions that outline the boundaries of the area from which the front of an antenna can intercept signals and deliver them to the output at relatively equal levels. Generally, the narrower the beamwidth of an antenna, the greater the directivity and gain.

Bi-directionalA 2-way device that is capable of passing signals from the cable telecommunications system to the customer, and from the customer back to the cable telecommunications system, usually in separate frequency ranges.  (See Two-Way)

Blocking (also called Block Errors or Error Blocking) – A common error in digital video transmission, especially in satellite video transmission. Blocking is usually displayed as empty black boxes in the displayed TV image.

Boot, Weather – See Weather Boot

CNR (Carrier to Noise Ratio) – A measurement that shows the difference in dB between the desired TV signal (the carrier) and the undesired noise, which is always present in any TV signal distribution system.  The greater the number, the better the expected performance.  A poor CNR will result in tiling and blocking in the TV image, and can cause total loss of any image information.  (See Noise and Noise Figure)

Coaxial Cable (coax) – A type of round transmission line composed of a central conductor (wire) surrounded in turn by an insulating material (dielectric), and a metallic shielding material which typically is an aluminum tape bonded to the dielectric and a wire braid providing 60% or better coverage of the tape which acts as the second conductor.  These elements, in turn, are covered by a thin layer of insulating and weatherproofing material such as PVC (polyvinylchloride). Coaxial cables used for home TV signal distribution have an impedance of 75 ohms.

Color Code, Antenna – See Antenna Color Code

Component Video – Typically used to interconnect a VCR, DVR, or other video source with a TV set, it is an analog video signal that is sent as three separate signals on three separate cables: Y for luminance and sync; PB for the difference between blue and luminance (B minus Y); and PR for the difference between red and luminance (R minus Y).  Component video cables are usually color-coded green for Y, blue for PB and red for PR. Component video provides higher video quality than composite video and S-video.  Audio information is not carried on component video cables.

Composite Video – Typically used to interconnect a VCR, DVR, or other video source with a TV set, the color information from an analog video signal is used to phase and amplitude modulate a color sub-carrier.  It is transmitted on one cable, which is usually color- coded yellow and uses an RCA connector. Composite video provides a lower video quality than S-video and component video.  Audio information is not carried on composite video cables.

Customer Premises Equipment (CPE) – Consumer electronic equipment such as a television set, converter (set-top box), satellite dish and receiver, home theater amplifier, etc., located in the consumer’s home.   

Decibel (dB) – A measurement term that describes the strength (level) of a signal in logarithmic relation to a reference strength (level).  For example, when the signal strength is expressed in micro-volts, an increase of the signal level by 3 dB means that the signal level has been doubled.

dBmV – A measurement term used to describe the absolute amount of power at a given point in a network, referenced to one millivolt across 75 ohms impedance.  This is the standard used to measure received TV signal levels in North America.

Dielectric – An insulating material placed between conductors to prevent the conductors from physically contacting one another (shorting out). In coaxial cable, insulating material surrounds the central conductor to prevent it from touching the metallic shield (and other conductor wire if one is used). The insulating material also maintains a specific amount of space between the central conductor and the other conductor. This spacing is necessary to maintain certain cable characteristics that if changed, will decrease the quality of the signal.

Digital Channel – This indicates the RF channel a TV station uses to transmit its programming.  This may be different than the channel number normally associated with a TV station prior to the conversion from analog to digital broadcasting.  During the conversion, TV stations on most low band VHF channels (those on channels 2-6), and all TV stations on channels 52 and above were reassigned new channels.  In addition, many other TV stations were also assigned different channels to use for their digital signals.  As a result, the actual RF channel a station transmits on may be different than the channel number TV viewers tuned to while the station was still broadcasting its analog signal.  Since the channel number is so closely identified with the TV station, most TV stations still use the original channel number, even though they may be transmitting on a different channel.  The virtual channel information is transmitted along with their programming.  Digital TV sets display the virtual channel number even though the TV set is actually tuned to the digital channel when that station is being viewed.  (See Virtual Channel)

Dipole – The element(s) of an antenna that intercepts the signal and feeds it to the antenna output terminals.  The other elements of the antenna serve as “directors” and “reflectors” which direct or reflect the incoming signal to the dipole element.

Directional Coupler – A device used in TV signal distribution networks to divide a single cable into two separate cables, abbreviated “DC”.  It typically will have low signal loss on one output, and higher signal loss on the other output.  The output with higher signal loss is typically called the “tap” output.  The value of the DC is given in dB, and represents the maximum expected signal loss from the input port to the tap output port.

Directivity – The ability of an antenna to pick up signals from one general direction (usually from the front) and effectively reject those from other directions (usually from the back and sides). The front-to-back ratio is one measure of an antenna’s directivity.

Discharge Unit, Antenna – See Antenna Discharge Unit

Distortion Beats – A distortion that occurs when two or more frequencies mix in a non-liner device or circuit, causing sum and difference frequencies and other combinations.  In analog video, this typically shows up as wavy lines in the picture. CSO (composite second order) and CTB (composite triple beat) are types of distortion beats.

Distribution Amplifier – An amplifier that is mounted indoors to boost the strength (level) of the received signal so that it can be fed to two or more receivers.  It is also sometimes called a drop amplifier.

Drip Loop – A short, U-shaped loop of a wire (or cable) immediately adjacent to a house entry point or electrical connection, so that water will drain off of the wire and not run into the house or connection.

Drop Amplifier – See Distribution Amplifier

Dual Tuner – Typical used in a DVR that has the ability to record two programs at the same time, or allows one program to be viewed while a second one is being recorded.  Most dual tuner DVRs also allow a pre-recorded program to be viewed while the two tuners are in use for recording other programs.

DVI Digital Video Interface – Designed originally as a digital replacement for the VGA standard used in analog TVs, DVI is a digital interface used to provide a digital interconnection between a computer and monitor, or between a TV set and Blu-ray players, DVD players, and set top boxes.  While it has largely been replaced by HDMI, DVI is still commonly seen on many devices. (See HDMI)

Digital Video Recorder (DVR) – A device used to store digital TV signals on a hard disk using an encrypted MPEG-2 format, it allows the viewer to pause and rewind live TV programming as well as record and play back programming at a later time.  Sometimes called a PVR (Personal Video Recorder), they have become a popular way to time shift TV viewing with higher quality than a VCR.   

Electromagnetic interference (EMI) – Interference into devices or TV signal transport systems caused by electrical noise created by faulty equipment, electrostatic discharge, lightning strikes, radio frequency interference, electrical power line noise, and many other electrical devices.

Element, Antenna – The small, hollow metal rods of various lengths that are attached (usually perpendicularly) to the main horizontal support member (boom or crossarm) of the antenna. The element at the rear of the antenna (called reflector) is usually the longest.  The element that actually feeds the intercepted signal to the antenna output is called a dipole.

Ethernet – A computer networking technology defined by IEEE 802.3 which is widely used for interconnecting computers, set top boxes, TV sets, and other devices to a home network that is then connected to the Internet.

F-Connector – A small, metallic, male-type connecting device with internal threads that attach to the end of a coaxial cable to secure and electrically connect the coax to a female F-fitting. The internal threads of the male connector screw onto the external threads of the female connector. Most baluns have a female-type F-connector on one end for the 75 ohm coax, and terminal lugs on the other end for 300 ohm twinlead.

Field Strength Meter – An electronic instrument that measures the strength of a signal and indicates it on a meter calibrated in microvolts (uV) or decibels (dB).  (See Microvolt/Decibel.)

Filter, High-Pass – See High-Pass Filter

Flatness – A measure of how close to the ideal specification the frequency response of a device or network actually performs.  (See “Frequency Response”)

FM – The term means frequency modulation. In relation to television and antenna systems, “FM” refers to the frequency modulated signal (FM radio stations whose frequencies are between TV channels 6 and 7).

Freezing (Freeze Frames) – An impairment where the picture appears to momentarily freeze or stop.  This is typically caused when a digital signal has too many errors for the receiver to correct, so the preceding frame is displayed until the receiver is able to display a new video frame.

Frequency Response – The gain/loss vs. frequency characteristics of a device or network. (See “Flatness”)

Front-to-Back Ratio – A measure of the directivity of an antenna that is based on the difference between the strengths of signals received from the antenna front and those received from the back. The difference usually is expressed in decibels (dB). For example, a front-to-back ratio of 40 dB indicates that the output strength (in uV) of signals received from the antenna front will be 100 times greater than those received from the back. Generally, the higher the rating in dB, the greater the directivity of the antenna.

Gain – An increase in signal strength, typically expressed in dB. The “gain” of an antenna indicates how much more signal strength it delivers to the output terminals than would a single element antenna (a dipole) under the same reception conditions. Antenna gain usually is expressed in decibels (dB). For example, an antenna with 10 dB gain will deliver 3.2 times more signal strength to the output terminals than will a single-element antenna.

Ghosts (ghosting) – Faint duplicate images that appear in a TV picture to either the left or right of the desired picture image.  This distortion was primarily an issue with analog broadcast signals and is not a major concern with current digital broadcast signals.

GHz – 1000 MHz (See “Hz”)

Ground Rod – A long metal rod that is driven into the ground near an antenna installation and to which is attached the grounding wires from the mast and antenna discharge unit to discharge static electricity to ground before it can enter and damage the TV receiver.  The National Electrical Code requires ground rods to be bonded to the home Ground Electrode System with #6 or larger copper wire.

Guy Wire (Guying) – Three or more multi-strand steel or aluminum wires that are connected between the guy ring(s) on the antenna mast and widely spaced eye screws in the house roof, supporting the mast against the forces of wind and ice.

Guy Ring – A circular metal collar with attachment holes (eyes) that is slipped on and clamped to an antenna mast. Guy wires are then attached to the mast through the holes in the guy ring.

HDMI, High-Definition Multimedia Interface – A compact audio/video interface for transmitting uncompressed digital data between a programming source and a display device, or between devices in a home theater network.  An HDMI interface can support standard, enhanced, and high definition uncompressed video, up to 8 channels of uncompressed or compressed digital audio, an Ethernet data connection, and a Consumer Electronics Control connection.  HDMI interfaces are typically seen on digital televisions sets, DVRs, video game consoles, DVD and Blu-ray players, set top boxes, PCs, PC monitors, camcorders, and video projectors. 

High Band (TV) – The band of frequencies assigned to VHF TV channels 7 through 13 by the Federal Communications Commission (FCC).

High-Pass Filter – A device that is connected to a transmission line to filter out interfering signals whose frequencies are below those in the TV band.  High-Pass Filters typically are used to filter out interference caused by Amateur and Citizens Band radio transmission.

Hz – Hertz - the basic unit of measurement for frequency. 

1 Hz = 1 cycle per second

60 Hz (standard line frequency rate in the US) = 60 cycles per second

1000 Hz = 1 kHz (kilohertz)

1000,000 Hz = 1000 kHz = 1 MHz (Megahertz)

1000,000,000 Hz = 1,000,000 kHz = 1000 MHz = 1 GHz (Gigahertz)

Impedance – A signal-affecting characteristic that is present to some degree in all electrical conductors (wires) and electronic circuits. Impedance is usually expressed as so many ohms. To prevent an unnecessary decrease in the strength of a signal that is being transferred (coupled) from one type of conductor or circuit to another, the difference in impedance must be “matched” by a device that compensates for the differences in impedance. A balun is used in antenna systems to compensate for the differences in impedance between a 300 ohm antenna and a 75 ohm coax, and between a 75 ohm coax and the 300 ohm input circuit of a TV receiver. Impedances that are not the same, or whose differences have not been compensated for, are said to be mismatched.

Input Capability, Preamp – The maximum strength of signal, in microvolts (uV), that an antenna preamp can accept without “overloading.” (Overloading causes distortion, reduction, or complete elimination of the signal.)

Insertion loss – Decrease of signal from the input of a device to the output of a device, or of a length of cable, expressed as dB loss.

Insulator, Acrylic – See Acrylic Insulator

KHz – 1000 Hz (See Hz)

Line, Transmission (TV) – See Transmission Line

Low Band (TV) – The band of frequencies assigned to VHF TV channels 2 through 6 by the Federal Communications Commission (FCC).

Low Pass Filter – A circuit or device that is designed to pass signals or channels below a specific frequency while blocking signals or channels above that frequency.

Lug, Terminal – See Terminal Lug

Mast, Antenna (TV) – A vertical section (or sections) of tubular steel or aluminum on which the antenna is mounted. Most sections typically are available in 5 and 10 ft. lengths.

Matching Impedance – See Impedance

Matching Transformer (TV) – See Balun

MHz – 1000 kHz (see Hz)

Microvolt (uV) – One millionth of a volt, or 0.000001 volt. The strength of the signals in a TV antenna system is expressed as so many microvolts (uV).  Generally, to produce an acceptable TV picture, the strength of the TV signals at the input terminals of a TV set must be at least 1000 microvolts (uV).

Mismatch, Impedance – See Impedance

Multiple Array – Two or more antennas mounted on the same mast with outputs coupled together.  Multiple arrays are used to increase gain (signal strength) and directivity.

National Electrical Code (NEC®) – Published by the National Fire Protection Association, the National Electrical Code, or NFPA 70, is an ANSI (American National Safety Institute) approved standard for the safe installation of electrical wiring and equipment.  While the NEC itself is not law, it is commonly adopted into law by states or localities and it specifies building grounding and bonding requirements, the type of coaxial cable to use in special interior applications such as plenum and risers, and a number of other subjects related to electrical and communications wiring in a home. 

National Television System Committee (NTSC) – The committee that defined the analog television system, known as NTSC, that was used in most of North America, South America, South Korea, Japan and the Philippines.  

Noise – A type of undesired signal present in all TV signal distribution systems.  In analog TV pictures, it shows up as “snow” in the picture.  In digital TV pictures, if there is too much noise, it can cause tiling and blocking of the image.  (See CNR)

Noise Figure – A method of specifying the amount of noise an amplifier will add to a network.  Generally, the lower this number, the better.  The lower the noise figure of a circuit, system, or component, the lower the output noise level will be compared to the output signal (the better the CNR will be).  (See CNR)

Ohm – The unit of measurement for resistance and impedance. (See Impedance)

Omni-directional (Antenna) – An antenna capable of intercepting signals from all compass directions equally well. Such an antenna is non-directional.

Operating temperature range – The temperature range over which devices are designed to operate properly.  For most TV signal distribution products intended to be used outdoors, this is –40˚ F to + 140˚ F (-40˚ C to +60˚ C).

Orient (an antenna) – To aim the antenna in a specific direction, usually toward the transmitting tower(s) of the TV stations.

Overloading of Preamp – See Input Capability, Preamp

Overloading of Receiver – See Receiver Overload (TV)

Passband – The range of frequencies a devices passes.  (see Bandpass and Bandwidth).

Passband Response – The response of a device throughout its entire passband. (See Frequency Response and Flatness)

Passive Device – Any signal-handling device (in an antenna installation) that is not electrically powered and therefore, does not increase the strength of the signal.  Passive devices will attenuate the RF signals by some amount.  Couplers and splitters are examples of passive devices.

Passive ReturnA 2-way device that does not have amplification in the return path.

Picture Carrier (TV) – The part of an analog TV signal that contains the video (picture) information.

Pitch Pad – A small piece of neoprene or other “rubbery” material that is placed under the legs of a tripod roof mount to cushion the mount and seal around the anchor bolts that secure the legs to the roof.

Plaster Strap – A non-metallic strap that is used to secure wall connectors for 300 ohm twinlead. (Metal straps cannot be used with twinlead because they affect its signal-handling characteristics.)

Plumb Bob – A metal weight (usually cone-shaped), that is attached to a length of cord or string and hung free from a height to determine whether the line between two points or the position of a vertical structure is truly vertical.

Polar Plot – A flat graph that provides a bird’s-eye view of antenna performance characteristics such as directivity and beamwidth.

Power Adapter – An electronic device used with amplifiers, preamplifiers, rotors, and other devices, to convert the incoming line voltage (120VAC in North America) to the regulated DC voltage needed to operate the device.

Power Inserter – A device used to combine RF and voltage onto the same coaxial cable to power devices that are not near power outlets. 

Preamplifier, TV (Preamp) – An amplifying device that is mounted on the mast or antenna boom as close to the antenna output terminals as possible, so that the strength of a very weak signal is increased (amplified) before it enters the transmission line.  Without this preamplification, the strength of the already weak signal would be further reduced as it passes through the transmission line producing tiling or blocking on the TV screen.

Radio Frequency (RF) Spectrum – The portion of the electromagnetic spectrum used for radio and television services.  It ranges from a few kilohertz to just below the frequency of infrared light. 

Radio Frequency Interference (RFI) – RFI is a subset of electromagnetic interference, and includes and interference to or from a device or system that is RF-related.   

Rafter – One of the parallel beams that form the slope of a roof

RCA Connector – This is commonly used on cables carrying audio, basedband video, component video, and composite video signals between different consumer devices.  It is also known as a phono connector.  

Rear Rejection – The ability of an antenna to reject (not receive) signals that approach it from the back.

Receiver Overload (TV) – A condition in which excessively strong signals cause analog pictures on analog TV receivers to lose synchronization (vertical and horizontal roll), have diagonal lines through the picture, or disappear completely.  On digital TV sets, receiver overload can cause tiling, blocking, and freezing of the image, or can make the image disappear completely.  In TV antenna systems, this is usually caused by using a preamplifier where it is not needed, or combining both a preamplifier and a distribution amplifier together when signal levels are already strong.

Return Loss – A measure of the amount of signal that is reflected back by a device.  Ideally, 100% of the energy applied to a device will pass through it.  In reality, a certain amount will always be reflected due to improper impedance matching between the two devices.  The percent of reflected energy, which is a different way of describing return loss, is typically very low.

Return Path – In a cable TV network, the portion of RF spectrum used for transporting signals from the customer to the headend, typically 5-42 MHz in North America.

RJ-11 – This is the standard connector used for 2-pair (4 wire) telephone wiring.  It is used to connect a telephone, telephone modem, or fax machine to the telephone wiring in a building.  Even though it has a total of six wire positions, usually only two or four are actually used.

RJ-45 – This is the standard connector used for 4-pair (8 wire) UTP (Unshielded Twisted Pair) cable including CAT- 5 and CAT-5e. It is used primarily for networking cables used for Ethernet, ISDN, T-1 and modern digital telephone systems.

Rotor Alignment Bearing – See Alignment Bearing, Rotor

Sensitivity, Antenna – General classifications of relative antenna gain used prior to the creation of the CEA Antenna Color Code, that indicates approximately how far from the station transmitter tower(s) an antenna designed to be used. Examples of these classifications are:

Deepest Fringe – 100+ miles for VHF and 60+ miles for UHF

Deep Fringe – 100 miles for VHF and 60 miles for UHF

Fringe – 80 miles for VHF and 45 miles for UHF

Near Fringe – 60 miles for VHF and 40 miles for UHF

Far Suburban – 50 miles for VHF and 35 miles for UHF

Suburban – 45 miles for VHF and 30 miles for UHF

Far Metropolitan – 30 miles for VHF and 25 miles for UHF

Metropolitan – 25 miles for VHF and 15 miles for UHF

Both sensitivity ratings and the CEA Color Code are based on optimum conditions over unobstructed terrain. What lies between a transmitter and an antenna installation will have a direct bearing on what type of antenna is appropriate.  Factors to consider are: the power output and height of a transmitting antenna tower, the type of terrain between the tower and the receiving antenna, and the size and number of buildings that lie in the path of the transmission.  (See Antenna Color Code)

Sound Carrier (TV) – The part of an analog TV signal that contains the audio (sound) information. (The picture information is contained in the picture carrier.)

Splitter – A device used to equally split the input signals into two or more output ports.  A 2-way splitter will have approximately 50% of the energy applied to the input port at each of the two output ports.  A 4-way splitter will have approximately 25% of the energy applied to the input port at each of the four output ports.  A special exception to this description is an unbalanced 3-way splitter.  It will have approximately 50% of the energy applied to the input port at the low loss output port, and will have 25% of the energy at the two high loss output ports.

Spurious Signals – Any undesired signals in a TV signal transportation system.  This can be created within the network, or can leak into the network from outside sources.

Standard Definition Television (SD or SDTV) – Developed by the ATSC, it is a digital television standard broadcast in a 4:3 aspect ratio, the same as NTSC.  It uses 480i resolution, and is not considered either enhanced-definition TV or high-definition TV.

S-Video – It is used primarily to interconnect consumer electronic devices, and its video quality is better than Composite Video, but not as good as Component Video.  It is an analog video transmission method that encodes the video on two channels: luma/intensity (Y), and chroma/color (C).  It does not carry audio information.   

Surge Withstand – The ability of a device to withstand a surge of a specific level.  Note that this does NOT suggest that it will protect anything connected to the device – it only describes its ability to continue to work after being subjected to a surge of a specific type and strength.

Standard Household Current (117V/AC) – The type of electrical power that is delivered to and operates appliances, lighting, electrical outlets and other electrical devices in a home. It is called alternating current (AC), and its normal value is 117 volts.

Standout (Standoff) – A metallic device with woodscrew threads or a clamp on one end and a circular loop (eye) with slotted insulating material on the other. It is used to secure and hold 300 ohm twinlead or other unshielded transmission line away from metal gutters, walls and other surfaces that can change the line’s signal-handling characteristics. The standout is screwed into a wall or other part of the house or is clamped onto the antenna mast. The transmission line then is inserted in the slot of the insulating material in the eye.

Star Bit – A steel, punch-like device that is hit with a hammer to “drill” holes through masonry (brick, cement block, etc.)

Switchable Trap – A small device that is used with a preamplifier to eliminate (trap out) unwanted signals. It is called “switchable” because it can be switched on or off (although this is difficult because the trap is mounted with the preamp up near the antenna). A switchable trap usually is used to eliminate the FM band.

Terminal Lug – A two-pronged connective device that is used to secure a wire to an electrical terminal. One end of the device is crimped onto the bare wire. The two flat prongs then are slipped around the terminal screw, and the screw head is tightened down against the prongs, securing the electrical connections.

Terminator – A device used to provide the characteristic impedance of the network on an unused port to stop the signals from reflecting back from that port.  If the port is open and not terminated, it essentially has 0 dB return loss, which means all the energy is reflected back into the network, which can have an impact on the performance.  Using a terminator on an unused port resolves this issue.

Tiling – This is a mosaic-like effect in the TV image which is caused by rectangular areas in the video image being displayed in the wrong position on the screen.  Low signal levels, extremely high signal levels, and high levels of interfering signals can all cause this effect.

Transmission Line – A two (or more) conductor wire that is used to carry current or signals from one point to another. Twinlead and coaxial cable are the most common types of transmission line used to carry TV signals from the antenna(s) to the receiver.

Tunable Trap – A small device that can be tuned (adjusted) to eliminate any frequency within a band. Tunable traps are frequently used with preamps, to eliminate a particularly troublesome signal.

Twinlead – A type of unshielded ribbon-like transmission line that consists of two insulated conductors (wire) separated by a thin, flat expanse of insulating material. TV twinlead has a characteristic impedance of 300 ohms, and therefore is called 300 ohm twinlead.

Two-WaySee Bi-Directional

UHF (TV) – UHF means ultra-high frequency. When used in relation to TV, UHF refers to channels 14 through 51, whose frequencies are located in the UHF band. Modern TV receivers are capable of tuning both VHF (channels 2 through 13) and UHF (channels 14 through 51).  Although the tuners of some television receivers can also be tuned to channels 52 through 83, there are no TV signals on these channels because the FCC has reassigned their frequencies to other uses.

UHF/VHF (TV) – An indication that a TV receiver or antenna is capable of receiving both the UHF and the VHF channels.

VHF (TV) – VHF means very-high frequency. When used in relation TV, VHF refers to channels 2 through 13, whose frequencies fall within the VHF band. The TV VHF band is divided into two subbands: (1) the low band, which includes channels 2 through 6 (a frequency range of 54 MHz-88 MHz), and (2) the high band, which includes channels 7 through 13 (a frequency range of 174 MHz-216 MHz). A portion of the frequency band between channels 6 and 7 is used for FM radio stations (88-108 MHz).

VHF/FM Broadband Antenna (TV) – A TV antenna that is capable of receiving the complete TV VHF band (channels 2-13) and also the FM band (88 MHz-108 MHz).

VHF/UHF/FM (TV) – An indication that a TV receiver or antenna is capable of receiving all VHF channels (2-13), all UHF channels (14-51), and FM band (88 MHz-108 MHz).  Some TV receivers, set top boxes, and antennas will still be rated for UHF reception on channels 14-69, or even channels 14-83.  This indicates that the device or antenna was originally produced while those channels were still in use for TV broadcasting.  Channels 52-83 have since been reallocated for other uses, and TV stations no longer use those channels.

Virtual Channel – This indicates the channel number normally associated with a TV station prior to the conversion from analog to digital broadcasting.  During the conversion, TV stations on most low band VHF channels (those on channels 2-6), and all TV stations on channels 52 and above were reassigned new channels.  In addition, many other TV stations were also assigned different channels to use for their digital signals.  As a result, the actual RF channel a station transmits on may be different than the channel number TV viewers tuned to while the station was still broadcasting its analog signal.  Since the channel number is so closely identified with the TV station, most TV stations still use the original channel number, even though they may be transmitting on a different channel.  The virtual channel information is transmitted along with their programming.  Digital TV sets display the virtual channel number even though the TV set is actually tuned to the digital channel when that station is being viewed.  (See Digital Channel)

Weather Boot – A rubber-like covering that is used to protect outdoor electrical connections from the weather (rain, ice, etc.).

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