Chapter 4 - Radio Frequency Signal and Antenna Concepts Flashcards
The installation of _____ has the greatest ability to affect whether or not the communication is successful.
antennas
To assist potential buyers with their purchasing decision, antenna manufacturers create _____ _____ and elevation charts, commonly known as _____ _____, for their antennas. These radiation patterns are created in controlled environments where the results cannot be skewed by outside influences and represent the signal pattern that is radiated by a particular model of antenna. These charts are commonly known as _____ or _____ _____ _____.
azimuth charts, radiation patterns, polar charts, antenna radiation envelopes
With an antenna, the radiation pattern will grow larger or smaller depending on how much power the antenna receives, but the shape and the relationships represented by the patterns will always _____ _____ _____.
stay the same
Remember that the logarithmic scale is a _____ scale, based on exponential values, so the polar chart is actually a visual representation using a _____ scale.
variable
_____ is the measurement of how broad or narrow the focus of an antenna is— and is measured both horizontally and vertically. It is the measurement from the center, or strongest point, of the antenna signal to each of the points along the horizontal and vertical axes where the signal decreases by half power (–3 dB).
Beamwidth
The –3 dB points are often referred to as _____-_____ _____. The distance between the two _____-_____ _____ on the horizontal axis is measured in degrees, giving the horizontal beamwidth measurement. The distance between the two _____-_____ _____ on the vertical axis is also measured in degrees, giving the vertical beamwidth measurement.
half-power points
It is important when aligning point-to-point antennas that you make sure they are actually aligned to the _____ lobe and not a _____ lobe.
main, side
There are _____ main categories of antennas.
3
_____ antennas radiate RF in a fashion similar to the way a table or floor lamp radiates light. They are designed to provide general coverage in all directions.
Omnidirectional
_____ antennas radiate RF in a fashion similar to the way a wall sconce radiates light away from the wall or the way a street lamp shines light down on a street or a parking lot, providing a directional light across a large area.
Semidirectional
_____ _____ antennas radiate RF in a fashion similar to the way a spotlight focuses light on a flag or a sign.
Highly directional
In addition to antennas acting as radiators and focusing signals that are being transmitted, they focus signals that are _____.
received
Omnidirectional antennas radiate RF signal in all directions. The small, rubber _____ antenna, often referred to as a rubber duck antenna, is the classic example of an omnidirectional antenna and is the default antenna of most access points.
dipole
The closest thing to an _____ _____ is the omnidirectional dipole antenna.
isotropic radiator
As it relates to omnidirectional dipole antennas, it is important to know that the higher the dBi or dBd value of an antenna, the more _____ the signal.
focused
The horizontal beamwidth of omnidirectional antennas is always _____ degrees, and the vertical beamwidth ranges from 7 to 80 degrees, depending on the particular antenna.
360
Indoor installations typically use low-gain omnidirectional antennas with gain of about _____ dBi.
2.14
Antennas are most effective when the length of the element is an _____ _____ (such as 1/4 or 1/2) or a multiple of the wavelength (l).
even fraction
Higher-gain omnidirectional antennas are typically constructed by stacking multiple dipole antennas on top of each other and are known as _____ _____.
collinear antennas
Omnidirectional antennas are typically used in _____-_____-_____ environments. The omnidirectional antenna is connected to a device (such as an access point) that is placed at the center of a group of client devices, providing central communications capabilities to the surrounding clients.
point-to-multipoint
It is common to use _____ antennas to provide a network bridge between two buildings in a campus environment or down the street from each other. Longer distances would be served by highly directional antennas.
semidirectional
What are the 3 types of semidirectional antennas?
Patch, Panel, Yagi
Patch and panel antennas, as shown in Figure 4.10, are more accurately classified or referred to as _____ antennas.
planar
Planar antennas can be used for outdoor _____-_____-_____ communications up to about a mile but are more commonly used as a central device to provide unidirectional coverage from the access point to the clients in an indoor environment. It is common for patch or panel antennas to be connected to access points to provide directional coverage within a building.
point-to-point