At a given azimuth, the minimum distance between the transmitting station and the closest point of return to the Earth of a transmitted wave reflected from the ionosphere.

An annular region within the transmission range of an antenna, within which signals from the transmitter are not received.
Note: The skip zone is bounded by the locus of the farthest points at which the ground wave can be received and the nearest points at which reflected sky waves can be received. Synonyms silent zone, zone of silence.

See Clipper

A radio wave that travels upward from the antenna.
Note: A sky wave may be reflected to Earth by the ionosphere.

Service Level Agreement

An electromagnetic waveguide (a) that consists solely of dielectric materials, (b) in which the dielectric propagation medium has a rectangular cross section, (c) that has a width, thickness, and refractive indices that determine the operating wavelength and the modes the guide will support beyond the equilibrium length, (d) that may be cladded, protected, distributed, and electronically controllable, and (e) that… (Read More →)

The action that occurs when a customer's long-distance telephone service (carrier selection) is switched from one long distance company to another without the customer's permission, and often, knowledge. [After FCC]

The line-of-sight distance between two points, not at the same level relative to a specific datum. [JP 1-02]
Note: An example of slant range is the distance to an airborne radar target, e.g., an airplane flying at high altitude with respect to that of the radar antenna. The slant range is the hypotenuse of the triangle represented by the altitude… (Read More →)

A clock that is coordinated with a master clock.
Note 1: Slave clock coordination is typically achieved by phase-locking the slave clock output signal to a signal coherent with, or whose clocking source is traceable to, the master clock.
Note 2: If it is necessary to adjust for the transit time of the signal from the master clock to the… (Read More →)

1. In a data network, a station that is selected and controlled by a master station.
Note: Usually a slave station can only call, or be called by, a master station.
2. In navigation systems using precise time dissemination, a station having a clock is synchronized by a remote master station. Synonym subordinate station.