Glossary

AM (Amplitude Modulation)
A method of impressing a signal on a radio carrier wave by varying its amplitude (different than frequency modulation).

Amplifier
Boosts the strength of an electronic signal.

Antenna
Transmits and receives radio and television signals. Depending on use and frequency, antennas can be a single piece of wire, dipole, a grid such as a yagi array, horn, helix, parabolic-shaped dish, or a combination of types.

Azimuth
The angle of rotation (horizontal) that a dish antenna must be rotated through to point to a specific satellite in orbit. The angle is a north to south line through the antenna’s location, measured in degrees clockwise.

Bandwidth
Measure of frequency use or capacity. Voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3KHz). Conventional TV channel occupies a bandwidth of 6 million cycles per second (6 MHz) in ground systems. Satellite based systems use a larger bandwidth of 17.5 to 72 MHz to spread or “dither” the signal to prevent interference.

Beamwidth
Angle or conical shape of the beam the antenna projects. Large antennas have narrower beamwidths and can pinpoint satellites more precisely in space or dense traffic areas on the earth. Tighter beamwidths deliver higher levels of power and better performance.

Broadband
Networks capable of delivering high bandwidth. Broadband networks were used by cable television, ranging from 550MHz to 1GHz. A single TV channel requires 6MHz. In digital satellite, bandwidth is measured in bits-per-second (BPS).

Coaxial Cable
Cable with an outer jacket, inner braid, foil, polyethylene core and copper center conductor. Used to connect TV or FM antennas with TV or FM receivers.

dB (Decibel)
A unit used to express the intensity of a sound wave, equal to 20 times the common logarithm of the ratio of the pressure produced by the sound wave to a reference pressure, usually .0002 microbar or 1 microbar.

DBS
Direct Broadcast Satellites, in the 12 GHz band range and beyond. Provides direct-to-home transmission.

Digital
Conversion of information into bits of data for transmission through wire, fiber optic cable, satellite, or over-air techniques.

Dish
Commonly used term for satellite antenna.

Downlink
Signal sent from communications satellite to the Earth station — your satellite dish.

Elevation
The upward tilt of a satellite antenna measured in degrees required to aim the antenna at the satellite.

Feed (Feedhorn)
The part of the antenna which collects the signal reflected from the dish surface and “feeds” it into the LNBF.

FM (Frequency Modulation)
Method of impressing a signal on a radio carrier wave by varying its frequency (different than amplitude modulation).

Footprint
Geographic area covered by satellite signal. Usually the signal is strongest at the center of the footprint and grows progressively weaker toward the edges.

Gain
Measure of amplification expressed in dB.

Geosynchronous or Geostationary orbit
The satellite arc or path (the Clarke Belt) in which domestic satellites are parked 22,237 miles above the equator. Satellites travel at the speed the earth rotates (7000 mph.), and appear to be stationary to a receiving dish.

GPS
Global Positioning Satellite. GPS systems use a group of satellites to triangulate exact position.

Impedance
The opposition a circuit offers to the flow alternating of current. it includes resistance and reactance andis measured in ohms.

LNB (Low Noise Block Downconverter)
A combination Low Noise Amplifier and downconverter built into one device attached to the feed. (A block converter simultaneously converts the entire frequencies of one polarity received by the dish to a lower frequency.)

LNBF
Integrated feed and LNB.

Megahertz (MHz)
Standard abbreviation for millions of cycles per second.

Multiplath Reception
Reception of FM or TV signals from different directions of different lengths due to obstructions, reflecting objects, etc. Causes “ghosting” on TV and distorted FM audio.

Modulator
A device which modulates a carrier; found as components in broadcasting transmitters and satellite transponders. Modulators are also used by CATV companies to place a baseband video television signal onto a desired VHF or UHF channel. Home VCRs have built-in modulators allowing recorded video played back using a television receiver turned to VHF channel 3 or 4.

Noise
Extraneous signals in a system causing interference (hum, hiss, rumble) and sound distortion.

Noise Figure (NF)
Measures the thermal noise contribution of LNAs and receiver front ends.

Parabolic Dish
Most frequently found satellite TV antenna, named for the shape of the dish described mathematically as a parabola. The parabolic shape focuses the weak microwave signal hitting the surface of the dish into a single focal point in front of the dish where the feedhorn is usually located.

Programmer
Originator of television programs transmitted via satellite.

Receiver
A “signal tuner,” receiving information from the LNB and converting it to a frequency which is displayed on your television screen; also allows you to tune to different TV channels.

RF (Radio Frequency)
Frequency of AM, 535-1605 KHz; FM, 88-108 MHz; TV, 54-806 MHz.

Satellite
Electronic communications relay station orbiting 22,237 miles about the equator, moving in a fixed orbit at the same speed and direction as Earth (about 7,000 mph east to west). Satellites relay audio/video signal to your receiver, where information is descrambled and converted.

Selectivity
Ability of receiver to reject transmissions from frequencies other than the specific one to which it is tuned.

Signal-to-Noise Ratio
Ratio of desired signal to unwanted noise. A high signal-to-noise ratio is highly desired. Difference of 45 dB is required for clear reception.

True North
Geographic north, determined by the earth’s axis. True north is one of the measurements used to align satellite antennas with the satellites. Magnetic north is determined by the earth’s magnetic poles.

Tuner
A device used in receivers or as a separate unit; receives radio signals and converts them into usable signals.

TVRO
An industry term meaning Television Receive Only. Describes antennas designed to receive satellite signals.

Uplink
An uplink facility receives information from a program provider (HBO, TNT, CNN, etc.), then a large uplink dish concentrates and transmits these outgoing signals to the satellite.