MidTerm Flashcards
Which organization defines the 802.11 standard for communication of wireless network devices?
IEEE
Lightning arrestors will defend against which of the following?
Transient currents
In the three layer network model, Wireless LAN Controllers are typically associated with which layer?
Core Layer
What is the frequency of a wave that cycles 2.4 billion times per second?
2.4 GHz
The distance between two equal points on a wave is known as ____________. This is typically measured from peak to peak between wave cycles.
Wavelength
If two waves of equal power arrive at a receiver exactly 180 degrees out of phase, they will _______________.
cancel each other out
Large groups of people in a single space can cause which issue with wireless signals?
Absorption
What is the EIRP in mW from a +3 dBi antenna attached to a 10mW radio?
20 mW
A standard measurement of frequency is called what?
Hertz
A 2.4 GHz signal will attenuate by approximately…
80 dB in the first 100 meters
Semidirectional antennas are often used for which of the following purposes? (Choose Two)
~ Providing short-distance point-to-point communications
~ Reducing reflections and the negative effects of multipath in warehouses
Which wave properties can be modulated to encode data? (Choose All That Apply)
~ Phase
~ Frequency
~ Amplitude
What is the approximate loss of a 2.4 GHz wave at 50 meters from the transmitter?
74 dB of loss
You have 4000 mW of power output from the antenna and you have 33 dB of free space path loss. What is your available power at the receiving antenna?
2 mW
The Intentional Radiator is:
Everything in the radio system up to, but not including, the antenna
Select the absolute units of power: (Choose three)
~ Watt
~ dBm
~ Milliwatt
In the three layer network model, wireless access points are located in which layer?
Access Layer
This abbreviation represents an absolute measurement of power referenced to one milliwatt:
dBm
An RF wave is bent while propagating from a high pressure area to a low pressure area. This is an example of:
Refraction
Which of these propagation behaviors can result in multipath? (Choose Four)
~ Reflection
~ Refraction
~ Diffraction
~ Scattering
The signal between the transceiver (radio) and the antenna will be reduced by which of the following? (Choose Three)
~ Adding an attenuator
~ Increasing the cable length
~ Using cheaper-quality cable
WLAN vendors use RSSI thresholds to trigger which radio card behaviors? (Choose Two)
~ Roaming
~ Dyanmic Rate Switching
If two waves of equal power arrive at a receiver exactly 180 degrees out of phase, they will _______________.
cancel each other out
An RF signal bounces off a large metal object (like an elevator). This is an example of:
Reflection
The alignment of two waves at a specific point in space and time is known as _________.
Phase
What is the definition of the horizontal beamwidth of an antenna?
The distance between the two -3 dB power points on the horizontal axis, measured in degrees
To double the maximum distance of a signal, the EIRP must be increased by how many decibels?
6 dB
When a long distance point-to-point link is installed, earth bulge should be considered beyond what distance?
7 miles
Which organization certifies that wireless devices conform to standards and are compatible with each other?
Wi-Fi Alliance
802.11 WLANs are designed for use in which type of frequency band?
Unlicensed
If you need an active amplifier, where in your system should it be installed for best performance?
Close to the antenna
Name the three layers of the “Three Layer Network Model”. (Choose Three)
~ Access
~ Core
~ Distribution
The signal strength that is transmitted from an antenna is known as what?
Equivalent Isotropically Radiated Power
When calculating link budget and system operating margin (SOM), padding the budget by reducing the receive sensitivity of the radios in the calculation is known as what?
Fade Margin
To double the strength or power of a signal, the EIRP must be increased by how many decibels?
3 dB
The carrier signal for 802.11 WLAN communications is?
Electromagnetic Waves
If you have a 100 mW 2.4 GHz radio with a 6 dBi antenna attached to an antenna cable with 2 dB of of insertion loss, what is your available power output from the antenna?
250 mW
A point source which radiates a signal equally in all directions and has 0dB of gain is known as what?
Isotropic radiator
In the three layer network model, wireless bridges are typically associated with which layer?
Distribution Layer
RF waves decrease in amplitude as they propagate from the antenna due to the broadening of the wave front. This is known as:
Free Space Path Loss
The Wi-Fi Alliance is a ________________.
Certification Organization
One watt is equal to:
1,000 mW
Which organization defines power output limitations of radio frequency devices operating in the USA?
FCC
An RF wave hits a chain link fence and multiple waves reflect in different directions. This is an example of:
Scattering
What term describes the time differential between a primary signal and a reflected signal arriving at a receiver?
Delay Spread
If you have a 90 mW 2.4 GHz radio with a 12 dBi antenna, what is your available power output from the antenna?
1440 mW
Which of the following VSWR measurements would provide the best signal to the antenna?
1.1:1
Which of the following devices produce active gain?
RF Amplifier
The number of wave cycles that occur in one second is known as _____________.
Frequency
The number of wave cycles that occur in one second is known as _____________.
Frequency
RF waves are:
Electromagnetic waves
You have 3 dBm of power at a distance of 12 meters. If you increase the distance to 48 meters, how much power will you have at the new distance?
-9 dBm
What are some results of multipath interference? (Choose Two)
~ Downfade
~ Intersymbol interference (data corruption)
Which antennas are highly directional? (Choose all that apply)
~ Parabolic Dish
~ Parabolic Grid
The size of the Fresnel zone is controlled by what factors? (Choose Two)
~ Distance
~ Frequency
Which of the following devices produce passive gain? (Choose all that apply)
~ Semidirectional Antenna
~ Parabolic Dish
Sector antennas are primarily used for what type of wireless communication?
Cellular Telephone
An RF wave hits a dense building material (like a brick wall) and some of the RF energy is converted to heat. This is an example of:
Absorption
RSSI metrics are used by 802.11 radios to measure which RF characteristic?
Signal Strength
A 2.4 GHz system with a power output of 77 dBm at the antenna has signal strength of -3 dBm at 100 meters. What will the signal strength be at 200 meters?
-9 dBm
0 dBm (zero dBm) is equal to:
1 mW
The 802.11a standard uses which frequency band?
5 GHz
The measurement of signal strength for a WLAN card uses an arbitrary scale of 0 to a maximum value of 255. What is this metric called?
RSSI
It is possible to have a measurement of signal strength in negative dBm (less than 0dBm).
True
______________ is the height or power of a wave.
Amplitude
The following is an Azimuth chart for which type of antenna?
Omnidirectional
Which of the following are true about antenna cables? (Choose Two)
~ They cause impedance on the signal
~ They add loss to the signal
The distance between two equal points on a wave is:
Wavelength
An antenna which broadcasts a signal 360 degrees horizontally is called:
Omnidirectional
Which three properties are interrelated? (Or put another way: Which three properties share a mathematical relationship?)
Frequency, wavelength and the speed of light
Which of the following statements are true? (Select TWO answers)
~ When the distance between an RF transmitter and receiver is cut in half, the wave gains 6dB of power.
~ When the distance between an RF transmitter and receiver is doubled, the wave loses 6dB of power.
The Institute of Electrical and Electronics Engineers (IEEE) is a ________________.
Standards Organization
When determining the mounting height of a long-distance point-to-point antenna, which of the following needs to be considered? (Choose Four)
~ Frequency
~ Earth Bulge
~ Distance
~ RF Line of Sight
Which RF component is responsible for generating the AC signal?
Transmitter
This abbreviation represents the power gain of an antenna relative to an isotropic radiator.
dBi
The ratio between the maximum peak voltage and minimum voltage on a line is known as what?
VSWR
The Fresnel zone should not be blocked by more then what percentage to maintain a reliable communications link?
40%
When calculating link budget, the difference between the actual received signal strength and the required signal indicated by the receive sensitivity is known as what?
System Operating Margin
You are setting up an outdoor point-to-point link using the 5.8 GHz band over a distance of 25 miles. The best antenna system to use for this link will be:
Parabolic Dish or Parabolic Grid Antenna
Electromagnetic waves…
can propagate through a vacuum.
When an RF signal bends around an object such as a building, this propagation behavior is known as what?
Diffraction
This is a relative expression and a measurement of change in power. It is used in wireless networking to measure gain or loss when comparing two signals.
dB
The 802.11b standard uses which frequency band?
2.4 GHz
Azimuth charts represent which of the following?
The horizontal plane of the RF signal propagation from an antenna on a logarithmic scale
The Federal Communications Commission (FCC) is a _____________.
Regulatory Domain Governing Body
Which of the following wireless communications parameters are typically governed by a local regulatory domain governing body? (Choose all that apply)
~ Maximum power of the intentional radiator (IR)
~ Maximum equivalent isotropically radiated power ~ (EIRP)
~ Bandwidth
~ Frequency
~ Indoor and/or outdoor use
You are a WLAN administrator and you have been asked to relocate an antenna approximately 200 feet away from the transmitting AP. You are concerned that a cable run of this distance will reduce the signal strength to a point where the output power at the antenna is not sufficient. What kind of device could potentially be installed in order to make up for the loss incurred from the 200 feet of cable?
Amplifier
A modulated signal capable of transmitting data is known as a __________.
Carrier Signal
One gigahertz is equal to:
1 billion cycles per second
802.11n uses which frequency bands? (Choose Two)
~ 2.4 GHz
~ 5.0 GHz
In a switched diversity system, the radio…
Samples both antennas and the uses the antenna with the best signal
What is the approximate loss of a 2.4 GHz wave at 400 meters from the transmitter?
92 dB of loss
You’ve installed an enterprise-class WLAN. You have provided outdoor access by placing an omnidirectional antenna in the center of a picnic area located on the corporate property. When you installed the outdoor antenna you also installed a lightening arrestor to protect your WLAN equipment. The antenna took a direct hit of lightning yesterday. What should you expect the result to be, since you’ve installed the lightning arrestor?
The antenna is likely destroyed and other equipment in-line may also be destroyed
Amplifiers can be purchased with which of the following features? (Choose All That Apply)
~ Fixed output
~ Bidirectional Amplification
~ Fixed Gain
~ Unidirectional Amplification
A data symbol is corrupted by multipath echos from the previous symbol. This is known as?
Intersymbol Interference
The IEEE 802.11 standard defines communication mechanisms at which layers of the OSI model? (Choose all that apply)
~ Data-Link (Layer 2)
~ Physical (Layer 1)
This abbreviation represents the value of the increase in gain of an antenna compared to a dipole antenna.
dBd
The 802.11g standard uses which frequency band?
2.4 GHz
Grid antennas are often preferable to parabolic dish antennas because…
Grid antennas are more resistant to the effects of wind
