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Active gain
created by a devices addition of electrical current to the signal (such as the transmitter or an amplifier
Passive gain
created by a devices shaping of the signal ( such as an antenna)
Beamwidth
the measure of how broad or narrow the focus of an antenna is, measuring both horizontally and vertically.
Omnidirectional Antenna
radiate rf signal in all direction
high gain OA vertical signal decreased and horizontal signal incresed
used in point to multipoint indoor enviroments
connect multiple buildings
make usre the gain is high enough to provide coverage
semidirectional antennas
signal in a specific direction
short to med distance communication
can be tilted downward toward area to be covered
3 types
patch panel yagi
Patch
outdoor point to point communication up to one mile
a central device to provide unidirectional coverage from the ap to the client
180 degree of horizontal beamwidth or less
prove coverage for long halways
yagi
support a vey narrow range of frequencies
length of elements vary according to the wavelength of different frequencies
used for short to medium distance point to point comunications up to 2 miles
high directional antennas
point to point communications
network bridging between 2 buildings
focused narrow beamwidth
highly affected by wind
types parabolic dish, grid
paraboilc dish
small digital satelite antenna
grid antenna
similar to barbecue with curves inward
the space between depends on the frequency
grid attenna in windy enviroments
phase array antennas
is multiple attenas that are onnected to a single processor
processor feeds individual antennas
transmit multiple beamwidths to mult users
expensive
sector antennas
high gain semidirectional antenna
pie shaped coverage pattern
installed in middle of area and placked back to back to eachother
together provide omnidirectional coverage
Fresnel zone
footballshaped area between two p2p antennas
no object to encroach more than 40% of fresnel zone
1st zone 0 to 90 degrees out of phase
2nd zone 90 to 270" "
3rd 270 to 450 " "
earth buldge
7 mies an issue
tree problems and mountains
antenna polorization
is the direction the electric field and is the same as the the physial attitude if the antenna
p2p bridge polarization is imporant
antenna diversity
helps to mitigate the effects of multipath
not used concurrently
multiple input multiple outpath (MIMO)
improve signal quality
uses multiple antennae concurrently
placement
omnidirectional antennas
places in the center of the coverage area
low gain provide broader vertical coverage
high gain much flatter coverage
directional
know both vertical and horizontal beamwidths
if to strong its a security risk
mounting
aesthetics and security
maintenance
preventive and diagonistic
voltage standing wave ratio VSWR
change to impedandces to an AC signal
signal from cables to the antenna
voltage reflection coefficient (rho)
ratio between voltage of the reflected wave and the voltage of the incdent antenna.
antenna accessories
cables, connectors, splitters, amplifier, attenuators, lighting arrestors
Author
Tjr31
ID
36077
Card Set
CWNA
Description
ch 4
Updated
2010-09-20T21:39:56Z
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