HACBSS

Homestead and community Broadcasting Satellite Service. Remote area DBS service via AUSSAT.

Hall Circuit

The uplink and downlink between the same earth station and a sattle.

Half-Transponder

A method oftransmitting two TV signals through a single transponder, by reducing the deviation and power allocated to each. TV carriers each operate typically 4 dB to 7 dB below single-carrier saturation power.

Hall Effect Sensor

A semiconductor device in which an output voltage is generated in response to the intensity of a magnetic field applied to a wire. In an actuator, the varying magnetic field is produced by the rotation of a permanent magnet past a thin wire. The pulses generated serve to count the number of rotations of the motor.

Hard Drawn Copper Wire

Copper wire that has not been annealed after drawing.

Hard-line

A low-loss coaxial cable that has a continuous had metal shield instead of a conductive braid around the outer perimeter. This type of cable was used in the pioneer days of satellite television.

HDTV

High-definition television.

Head Unit

Alternative term for an LNA, LNB, or LNC. Also called the outdoor unit.

Headend

Central distribution point for a CATV or MATV system. i.e. The portion of an SMATV system where all desired signals are received and processed for subsequent distribution.

Heliax

A thick low-loss cable used at high frequencies; also known as hard-line.

Hemispheric Beam

Shaped beam covering approximatelyhalf of the visible Earth's surface (21 percent of the total globe), as seen from the satellite. INTELSAT spacecraft carry east and west hemispheric beams, while Russian Gorizont and Raduga satellites are equipped with northern hemispheric beams illuminating the visible portion of the globe which lies north of the equator.

HEMT

High Electron Mobility Transistor.

Hertz

The name given to the basic measure of radio frequency. An electromagnetic wave completes a full oscillation from its positive to its negative pole and back again in what is known as a cycle. A single Hertz is thus equal to one cycle per second.

Hi-Pot

A term designed to determine the highest voltage that can be applied to a conductor without breaking through the insulation.

High Definition Television (HDTV)

An innovative television format having approximately twice the number of scan lines in order to improve picture resolution and viewing quality.

High Power Amplifier (HPA)

An amplifier used to amplify the uplink signal

High Power Satellite

Satellite with transponder RF power in excess of about 100 watts.

Horizontal Blanking Pulse

The pulse that occurs between each horizontal scan line and existinguishes the beam illumination during the retrace period.

Horizontal Sync Pulse

A 5.08 microsecond (4.7 microsecond in the PAL system) rectangular pulse riding on to of each horizontal blanking pulse. It synchronizes the horzontal scanning at the television set with that of the television camera.

Hour Angle

Angle between antenna beam and meridian plane (measured in equatorial plane). Steering direction of a polar mount antenna.

HPA

High-Power amplifier (esp. in an upline). Usually a TWTA or a Klystron.

HPF

High-Pass Filter.

Hue

Spectral tint parameter in a color video signal.

Hum Bars

A form of interference seen as horizontal bars or black regions passing across the field of a television screen.

Hypalon

Dupont's trade name for their chlorosuifonated polyethylene, an ozone resistant synthetic rubber.