AvMesh
®
RF Communications Systems
Installation & Service Manual
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5
1.0 Glossary of Terms
Attenuation -
The negative ratio of the output power to the input power in decibels
(dB). It is the reduction in power of a signal as it propagates through space.
Carrier signal -
a pure wave of constant frequency, amplitude and phase.
Centre frequency -
The central frequency of a filter or channel, centered between the
upper and lower cutoff frequencies.
Fresnel Zone -
A theoretical elliptical region between the transmitting and receiving
antennas. The size of the ellipse is determined by the frequency of operation and the
distance between the transmitter and receiver. If 80% of the first Fresnel Zone is free of
obstacles, the propagation loss is said to be equivalent to free space loss.
Gain -
The positive ratio of the output power to the input power in decibels (dB).
Interference -
Any external factor (such as physical obstacles, noise or other radio
signals) that degrade or reduce the clarity of the desired radio signal.
Light group -
A way to group lights in an area so that they can be controlled in unison.
This allows the airfield to independently control different areas such as multiple run-
ways, taxiways and helipads.
Listen only light -
A light that will receive commands and act upon them, but will not
pass the commands on.
Mesh network -
A local network architecture in which the nodes connect to as many
nodes as possible and cooperate with one another to transfer data from point to point.
Noise floor -
This is the measure of signal created from noise sources and unwanted
signals, with noise defined as a signal other than that being monitored. It may include
atmospheric noise, thermal noise and cosmic noise.
Passband -
The range of frequencies that can pass through a filter without attenuation.
Primary Node -
A light that is part of the primary AvMesh
TM
network. This light will
receive commands from a controller, other primary node or a reserve node. This light
will act upon the commands and pass them on to other nodes in the network.
Reference level -
The top most line in the spectrum analyzer display.
Reserve node -
A light that is part of the reserve AvMesh
TM
network. This light will
receive commands from a controller, a primary node or another reserve node. This
light will act upon the commands and pass them on to other nodes in the network.
RF Propagation -
The behavior in which radio waves travel from one point to another.
Sensitivity -
The smallest signal that can be detected by the receiver.
Selectivity -
The ability of a receiver to differentiate between signals that are close
together in frequency.
Span -
The range between the measured start and stop frequencies.
Spectrum analyzer -
An electronic measurement device that helps to determine the
type and frequencies of interfering RF signals.
Transmit Power -
The power that is input to the antenna cable, before cable loss and
antenna gain are considered.
