p.f.d. (or PFD)

Power-flux Density (related to field strength)

Packet Switching

The transfer of data by means of addressed packets whereby a channel is only occur for the duration of transmission of the packet. The channel is then available for the transfer of other pack.

Pad

A concrete base upon which a supporting pole and antenna can be mounted.

PAL

Phase Alternation System - the German developed TV standard based upon 50 cycles.per second and 625 lines.

Palapa

Indonesia / ASEAN regional satellite system.

Parabola

The geometric shape that has the property of reflecting all signals parallel to its axis to one point, the focal point.

Paraboloid

A parabola of revolution. Classical shape of a satellite antenna's reflector.

Paramp

Parametric Amplifier. Sophisticated type of LNA.

Path Loss

The attenuation that a signal undergoes in travelling over a path between two points. Path loss varies inversely as the square of the distance traveled.

Pay-Per-View

Pay-per-view is a method of purchasing programming one a per-program basis.

PCM

Pulse Code Modulation. Coding system for digital audio transmission.

PCS

Personal Communications Service. New digital wireless telephone technology, with smaller and less expensive outdoor cells and consumer telephone sets than current cellular service. Cable television operators are among the entrepreneurs for PCS. Also called PCN (Personal Communications Network).

PE

Pre-emphasis.

Peltier

Thermoelectric cooling system for cryogenic INAS.

Percent Conductivity

Conductivity of a material expressed as a percentage of that of copper.

Perigee

Lowest point (minimum altitude) of a geocentric orbit.

Periodicity

The uniformly spaced variations in the insulation diameter of a transmission cable that result in reflections of a signal, when its wavelength or a multiple thereof is equal to the distance between two diameter variations.

Persistence of Vision

The physiological phenomena whereby a human eye retains perception of an image for a short time after the image is no longer visible.

Phase

A measure of the relative position of a signal relative to a reference expressed in degrees.

Phase Distortion

A distortion of the phase component of a signal. This occurs when the phase shift of an amplifier is not proportional to frequency over the design bandwidth.

Pick

Distance between two adjacent crossover points of braid filaments. The measurement in picks per inch indicates the degree of coverage.

Pico

A numerical prefix denoting one-millionth of one-millionth (10 (12)).

Picture Detail

The number of picture elements resolved on a television picture screen. More "crisp" pictures result as the number of picture elements is increased.

Pitch

In flat cable, the nominal distance between the index edges of two adjacent conductors.

Planar Array

Flat satellite antenna composed of a gridwork of tiny resonant elements.

Plasticizer

A chemical agent added to plastics to make them softer and more pliable.

PLL

Phase Locked Loop (type of demodulator) Pulse width modulation.

PM

Phase modulation

Point-to-Point

A communications line connected directly from one point to one other point as opposed to multipoints lines.

Polar Orbit

An orbital path located along the plane of the Earth's polar axis.

Polar Mount

Antenna mechanism permitting steering along the geostationary Arc (Clarke Orbit) by rotation about a single axis. Also Equatorial Mount. A classical polar mount has its axis parallel to that of the Earth. Satellite receiving antennas use modified polar mount geometry, incorporating a declination offset.

Polarization

A characteristic of the electromagnetic wave. Four senses of polarization are used in satellite transmissions: horizontal; vertical; right-hand circular; and left-hand circular.

Polarization rot(at)or

A birefringent component in a waveguide or antenna system, which converts between linear (plane) and circular pofarizations. Not a polarization rotor.

Polarotor

A proprietary name for a type of polarization rotor, a transition with a remotely-rotatble probe.

Polymer

A material of high molecular weight formed by the chemical union of rnonomers.

Polyolefin

Any of the polymers and copolymers of the ethylene family of hydrocarbons.

Positive Picture Phase

Positioning of the composite video signal so that the maximum point of the sync pulses is at zero voltage. The brightest illumination is caused by the most positive voitages.

PPV

Pay-per-view. A system by which a viewer can pay and view the programme he wants from a programming menu.

Pre-emphasis

A method of improving SINR in an FM system, by increasing deviation at high (relative to low) baseband frequencies, according to a defined function.

Preamplifier

The first amplification stage. In an SMATV system, it is the amplifier mounted adjacent to an antenna to increase a weak signal prior to its processing at the headened.

Preemptive transponder

A transponder which is sold or leased under the condition that it can be supplied in an emergency to primary customers which have leased or purchased protected transponders from the selling or leasing entity.

Proton

Soviet D-class heavy launch vehicle (used for Statsionar flights).

Primary Colors

Red, green and blue.

Prime focus Antenna

A parabolic dish having the feed/LNA assembly at the focal point directly in the front of the antenna. Prograde : being or relating to orbital or rotational motion of a body that is in the same direction as it another celestial body (Also see Geosynchronous).

Protected Transponder

Entities which lease or purchase protected transponders are guaranteed acce the supplier to a backup transponder in the event that the primary transponder fails. (Also see preem transponder).

PSD

An abbreviation for polarity selection device.

PSK

Phase-shift Keying (type of digital modulation).

Psophometry

A type of channel noise measurement.

PWM

An audio transmission format used by the Russians to transmit the TVs signals within the video's horizontal blanking interval.

Pulse and Bar

A video test waveform, included in ITS.