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CWNA practice questions

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Question 1Radio Frequency (RF) Technologies

What is the approximate free-space wavelength of a 2.4 GHz signal?

  1. 1.25 m
  2. 3.0 cm
  3. 12.5 cm Correct answer.
  4. 25 cm

Explanation

Wavelength equals the speed of light divided by frequency, so 300,000,000 m/s divided by 2,400,000,000 Hz gives about 0.125 m, or 12.5 cm. Higher frequencies produce shorter wavelengths, which is why 5 GHz signals are roughly half this length.

Question 2Radio Frequency (RF) Technologies

An antenna is rated at 10 dBd. What is its equivalent gain in dBi?

  1. 7.86 dBi
  2. 20 dBi
  3. 8.14 dBi
  4. 12.14 dBi Correct answer.

Explanation

The dBi scale references an isotropic radiator, while dBd references a half-wave dipole that already has 2.14 dBi of gain. Converting requires adding 2.14 to the dBd value, so 10 dBd equals 12.14 dBi.

Question 3Radio Frequency (RF) Technologies

The unit dBm expresses absolute power relative to which reference?

  1. 1 microwatt
  2. 1 milliwatt Correct answer.
  3. 1 watt
  4. an isotropic radiator

Explanation

The suffix 'm' in dBm stands for milliwatt, so 0 dBm equals 1 mW and every 10 dB represents a tenfold change from that reference. Because it is an absolute unit, dBm values describe a definite power level rather than a ratio.

Question 4Radio Frequency (RF) Technologies

Which propagation behavior primarily explains the reduced signal level after RF passes through a thick brick wall?

  1. Diffraction
  2. Scattering
  3. Absorption Correct answer.
  4. Reflection

Explanation

Absorption converts RF energy into heat inside a material, so the signal that emerges from the far side of the wall is weaker than the signal that entered it. The amount of loss depends on the material, its thickness, and the frequency of the signal.

Question 5Radio Frequency (RF) Technologies

Compared with the 2.4 GHz band, what is a key characteristic of the 5 GHz band?

  1. It penetrates walls with lower loss
  2. It has more non-overlapping channels Correct answer.
  3. It allows only three non-overlapping channels
  4. It supports narrower maximum channel widths

Explanation

The 5 GHz band contains far more spectrum than 2.4 GHz, so many more channels can be used without overlapping, especially when bonding channels. The trade-off is higher free-space and material loss, which shortens usable range.

Question 6Radio Frequency (RF) Technologies

For a point-to-point link to behave approximately like free space, what minimum portion of the first Fresnel zone should be clear of obstructions?

  1. 60 percent Correct answer.
  2. 40 percent
  3. 20 percent
  4. 100 percent

Explanation

Keeping at least 60 percent of the first Fresnel zone unobstructed is the usual design guideline for point-to-point links. Clearing less of the zone introduces obstruction loss and makes the path behave less like free space.

Question 7Radio Frequency (RF) Technologies

Which antenna type radiates RF energy roughly equally in all horizontal directions?

  1. Dish
  2. Patch
  3. Yagi
  4. Dipole Correct answer.

Explanation

A dipole is an omnidirectional antenna, spreading energy in a 360-degree pattern around its axis with a null directly above and below. This makes it well suited to covering clients scattered around an access point.

Question 8Radio Frequency (RF) Technologies

What term describes the time difference between the first arriving signal and the last significant echo at a receiver?

  1. Guard interval
  2. Coherence bandwidth
  3. Doppler spread
  4. Delay spread Correct answer.

Explanation

Delay spread quantifies how much arrival times differ among multipath copies of the same transmission. Large delay spread increases the risk of inter-symbol interference if it approaches the symbol duration.

Question 9Radio Frequency (RF) Technologies

A signal traveling from air into a denser medium such as water changes direction at the boundary. Which term describes this?

  1. Scattering
  2. Refraction Correct answer.
  3. Reflection
  4. Diffraction

Explanation

Refraction is the bending of a wave as it passes between media with different propagation velocities, caused by the change in density. The change in direction can create coverage where line of sight does not exist.

Question 10Radio Frequency (RF) Technologies

A signal bends around the edge of a metal rooftop and reaches an area behind the building. Which propagation mechanism is this?

  1. Reflection
  2. Diffraction Correct answer.
  3. Absorption
  4. Refraction

Explanation

Diffraction occurs when a wave encounters the sharp edge of an obstruction and spreads into the shadowed region behind it. This is why some signal can be received even when the direct path is blocked.

Question 11Radio Frequency (RF) Technologies

Which environment most strongly produces scattering of a Wi-Fi signal?

  1. Rain and dense foliage Correct answer.
  2. An open parking lot
  3. A large flat metal wall
  4. A smooth glass window

Explanation

Scattering occurs when a wave strikes objects that are small relative to its wavelength or when a surface is rough, causing energy to disperse in many directions. Rain, foliage, and textured surfaces are common scattering sources.

Question 12Radio Frequency (RF) Technologies

A signal measures 20 mW at a point in the system. After a 6 dB loss, what is the approximate power?

  1. 10 mW
  2. 5 mW Correct answer.
  3. 2.5 mW
  4. 40 mW

Explanation

Using the 3 dB and 10 dB rules, a 6 dB loss equals two successive 3 dB reductions, and each 3 dB halves the power. Halving 20 mW twice yields 5 mW.

Question 13Radio Frequency (RF) Technologies

An access point transmits at 20 dBm into an antenna with 8 dBi of gain through a cable with 2 dB of loss. What is the EIRP?

  1. 26 dBm Correct answer.
  2. 24 dBm
  3. 28 dBm
  4. 30 dBm

Explanation

EIRP is the transmitter output plus antenna gain minus cable and connector losses, so 20 + 8 - 2 equals 26 dBm. This value must remain within the regulatory limit for the band and country of operation.

Question 14Radio Frequency (RF) Technologies

A high VSWR reading at the antenna connector indicates which condition?

  1. Insufficient channel width
  2. An impedance mismatch Correct answer.
  3. Excessive antenna gain
  4. A perfect impedance match

Explanation

VSWR measures how much energy is reflected because the antenna and transmission line impedances do not match. A high ratio means more power returns to the transmitter and less is radiated, which can also stress the radio.

Question 15Radio Frequency (RF) Technologies

A receiver measures a signal at -72 dBm and a noise floor of -92 dBm. What is the signal-to-noise ratio?

  1. 20 dB Correct answer.
  2. 10 dB
  3. -20 dB
  4. 164 dB

Explanation

SNR is the difference in dB between the received signal level and the noise floor, so -72 minus -92 equals 20 dB. Higher SNR values allow more complex modulation and coding to be used reliably.

Question 16Radio Frequency (RF) Technologies

Increasing a channel width from 40 MHz to 80 MHz has which effect on the noise floor in that channel?

  1. Raises it by 3 dB Correct answer.
  2. Leaves it unchanged
  3. Lowers it by 6 dB
  4. Lowers it by 3 dB

Explanation

A receiver captures noise across its entire channel, so doubling the bandwidth captures twice as much noise power, which is a 3 dB increase. The wider channel can carry more data but yields a lower SNR for the same signal level.

Question 17Radio Frequency (RF) Technologies

An access point antenna is vertically polarized while a client antenna is horizontally polarized. What is the typical outcome?

  1. Automatic conversion to circular polarization
  2. No effect on link quality
  3. Increased gain from alignment
  4. Significant polarization mismatch loss Correct answer.

Explanation

Two linear antennas oriented 90 degrees apart are cross-polarized, and a large portion of the signal is not received. Aligning the polarization of both ends avoids this avoidable loss.

Question 18Radio Frequency (RF) Technologies

What is the purpose of a fade margin in a wireless link budget?

  1. To account for unpredictable fading Correct answer.
  2. To halve the occupied channel width
  3. To increase the effective antenna gain
  4. To reduce the required cable length

Explanation

A fade margin is extra received signal power budgeted above the minimum required level so the link survives temporary fluctuations from weather, multipath, or interference. Without it, a link designed exactly at threshold would drop during ordinary fading events.

Question 19Radio Frequency (RF) Technologies

What is a key RF advantage of the 6 GHz band for Wi-Fi operation?

  1. It is limited to three non-overlapping channels
  2. It uses narrower channels than 5 GHz
  3. It penetrates walls better than 2.4 GHz
  4. It offers many wide channels free of legacy interference Correct answer.

Explanation

The 6 GHz band provides a large block of new spectrum, allowing numerous 20, 40, 80, and 160 MHz channels that are not shared with older Wi-Fi devices. The trade-off is greater path loss and poorer penetration than lower bands.

Question 20Radio Frequency (RF) Technologies

In free space, how much additional path loss results when the distance between transmitter and receiver is quadrupled?

  1. 12 dB Correct answer.
  2. 6 dB
  3. 3 dB
  4. 18 dB

Explanation

Free-space path loss rises 6 dB each time the distance doubles, because the 6 dB rule applies per doubling. Quadrupling the distance is two doublings, so the added loss is 12 dB.

Question 21Radio Frequency (RF) Technologies

Why does 1024-QAM require a higher SNR than 64-QAM?

  1. Its constellation states are spaced more closely Correct answer.
  2. It occupies a wider channel bandwidth
  3. It uses fewer subcarriers per channel
  4. It relies on a longer guard interval

Explanation

Higher-order modulation packs more bits into each symbol by placing constellation points nearer to one another. Closer points are more easily pushed across a decision boundary by noise, so a cleaner channel is needed.

Question 22Radio Frequency (RF) Technologies

Spatial multiplexing gains in a MIMO system depend most directly on which condition?

  1. Operation with a single spatial stream
  2. A narrower channel than the client supports
  3. Multipath with low spatial correlation Correct answer.
  4. An unobstructed line of sight with no reflections

Explanation

Spatial multiplexing sends independent data streams on the same channel, which requires the paths to be distinguishable at the receiver. Rich multipath with low correlation between antennas lets the receiver separate the streams.

Question 23Radio Frequency (RF) Technologies

What is the main purpose of the guard interval in an OFDM transmission?

  1. To prevent inter-symbol interference from delayed echoes Correct answer.
  2. To increase the transmit power
  3. To separate 2.4 GHz from 5 GHz channels
  4. To encrypt the preamble

Explanation

OFDM symbols are preceded by a guard interval, usually a cyclic prefix copy of the symbol's end, so late-arriving echoes finish before the next symbol begins. Choosing a guard interval appropriate to the environment's delay spread keeps symbols from overlapping.

Question 24Antenna Concepts

An access point radio transmits at 20 dBm. The cable and connectors between the radio and the antenna introduce 2 dB of loss, and the antenna has 9 dBi of gain. What is the EIRP of this system?

  1. 27 dBm Correct answer.
  2. 29 dBm
  3. 11 dBm
  4. 31 dBm

Explanation

EIRP is the radio output power plus antenna gain minus any cable and connector loss between the radio and the antenna. Here 20 dBm + 9 dBi − 2 dB = 27 dBm.

Question 25Antenna Concepts

An antenna datasheet lists a gain of 9 dBd. What is that gain expressed in dBi?

  1. 6.86 dBi
  2. 11.14 dBi Correct answer.
  3. 9 dBi
  4. 19.3 dBi

Explanation

The dBd reference is the half-wave dipole, which has 2.14 dBi of gain over an isotropic radiator. To convert dBd to dBi, add 2.14, so 9 + 2.14 = 11.14 dBi.

Question 26Antenna Concepts

What is the gain of a half-wave dipole antenna relative to an isotropic radiator?

  1. 0 dBi
  2. 1.5 dBi
  3. 3 dBi
  4. 2.14 dBi Correct answer.

Explanation

A half-wave dipole has 2.14 dBi of gain compared with a theoretical isotropic radiator, which is why 0 dBd equals 2.14 dBi. This value is the fixed offset used to convert between the two gain references.

Question 27Antenna Concepts

Two passive antennas are fed the same amount of RF power. One has a 30-degree beamwidth and the other has a 90-degree beamwidth. Which statement about gain in the peak direction is correct?

  1. Neither, because passive antennas always have equal gain at any beamwidth
  2. The 90-degree antenna, because a wider beam spreads energy over a larger area and therefore reaches farther
  3. Both, because gain depends only on the physical length of the antenna
  4. The 30-degree antenna, because the same energy is concentrated into a smaller area Correct answer.

Explanation

Gain and beamwidth are inversely related: as radiated energy is squeezed into a narrower pattern, the power density in the peak direction rises. With equal input power, the narrower 30-degree pattern therefore produces higher gain in its main lobe.

Question 28Antenna Concepts

An access point uses a horizontally polarized antenna while a client uses a vertically polarized antenna. What is the effect on the link?

  1. The antennas automatically convert to circular polarization to compensate
  2. There is no measurable effect, because polarization matters only for satellite links
  3. A large loss occurs, commonly on the order of 20 dB or more Correct answer.
  4. The received signal increases, because cross-polarization adds a second signal path

Explanation

Antennas must be polarization-aligned to couple efficiently; mismatched linear polarizations greatly reduce the signal that reaches the receiver. Cross-polarization discrimination on the order of 20 dB or more is typical for WLAN antennas.

Question 29Antenna Concepts

Which antenna radiates roughly equally in all horizontal directions and is typically used to provide 360 degrees of coverage from a central location?

  1. A grid
  2. An omni Correct answer.
  3. A Yagi
  4. A panel

Explanation

An omnidirectional antenna has a circular azimuth pattern, so it provides coverage in all directions around the mounting point. Its gain is concentrated by compressing the vertical pattern rather than by narrowing the horizontal pattern.

Question 30Antenna Concepts

What VSWR reading indicates a perfect impedance match between the radio and the antenna system?

  1. 0:1
  2. 1.5:1
  3. 2:1
  4. 1:1 Correct answer.

Explanation

VSWR is the ratio of maximum to minimum voltage on the feed line; a ratio of 1:1 means no reflected power and a perfect match. Real systems approach but rarely reach this ideal.

Question 31Antenna Concepts

What percentage of the first Fresnel zone is generally recommended to be kept clear of obstructions on a point-to-point link?

  1. 100 percent
  2. 40 percent
  3. 60 percent Correct answer.
  4. 20 percent

Explanation

The first Fresnel zone is the elliptical volume around the line-of-sight path that carries part of the signal energy. Best practice is to keep at least 60 percent of that zone free of obstructions to avoid diffraction loss; clearing the full zone is rarely practical.

Question 32Antenna Concepts

Antenna gain is described as passive. What does that mean?

  1. It uses an internal amplifier to boost the RF signal before radiation
  2. It lowers the loss of the coaxial cable feeding it
  3. It focuses existing RF energy into a narrower pattern Correct answer.
  4. It converts a portion of the RF energy into usable DC power

Explanation

A passive antenna does not create RF energy; it reshapes the radiation pattern so more energy goes in desired directions and less elsewhere. The apparent gain is a result of directivity, not amplification.

Question 33Antenna Concepts

What is the purpose of applying downtilt to a sector antenna mounted on a tall mast in a dense deployment?

  1. It tilts the main lobe downward to limit spillover into other cells Correct answer.
  2. It increases gain by widening the vertical beamwidth of the antenna
  3. It changes the antenna's linear polarization into circular polarization
  4. It raises the antenna's effective height above the surrounding clutter

Explanation

Downtilt aims the vertical main lobe toward the intended coverage area on the ground. This reduces energy radiated toward the horizon and beyond the cell edge, lowering interference with neighboring cells.

Question 34Antenna Concepts

If the distance between a transmitter and a receiver in free space is doubled, how much additional path loss is introduced?

  1. 12 dB
  2. 3 dB
  3. 6 dB Correct answer.
  4. 0 dB

Explanation

Free-space path loss follows a 20 log(d) relationship, so each doubling of distance adds about 6 dB of loss. Quadrupling the distance would add about 12 dB.

Question 35Antenna Concepts

An antenna system has a return loss of 10 dB. What percentage of the forward power is reflected back toward the transmitter?

  1. 90 percent
  2. 10 percent Correct answer.
  3. 50 percent
  4. 1 percent

Explanation

Return loss in dB equals −10 log(reflected power / forward power). A 10 dB return loss means one tenth of the forward power is reflected, which is 10 percent.

Question 36Antenna Concepts

A WLAN site uses three sector antennas, each covering 120 degrees, mounted at the same location. What is the primary benefit of this design?

  1. It removes the need for a wired backhaul to the distribution system
  2. It divides coverage into smaller cells, adding capacity Correct answer.
  3. It converts the site from access coverage to a point-to-point bridge
  4. It doubles the transmit power radiated in every horizontal direction

Explanation

Sectorizing replaces one wide coverage area with several narrower ones, each served by a higher-gain directional antenna. Smaller cells allow more frequent channel reuse and reduce contention and interference among clients.

Question 37Antenna Concepts

Which set of elements describes the construction of a Yagi-Uda antenna?

  1. A single driven element facing a large parabolic reflector
  2. One driven element, one reflector, and one or more directors Correct answer.
  3. Several patch elements printed on a grounded dielectric slab
  4. Two driven elements fed 90 degrees out of phase with each other

Explanation

A Yagi-Uda antenna consists of a driven element, a slightly longer reflector placed behind it, and one or more shorter directors in front. Adding directors increases directivity in the forward direction.

Question 38Antenna Concepts

Which condition is required to obtain spatial multiplexing gain from a MIMO access point?

  1. A single spatial stream transmitted from one highly directional antenna
  2. A clear line-of-sight path with no reflections or scattering
  3. Both antennas receiving identical signals that are perfectly in phase
  4. Low correlation between the signals arriving at each antenna Correct answer.

Explanation

Spatial multiplexing sends independent data streams on separate antennas and depends on the receiver being able to separate them. That separation is possible when the signals at each antenna are sufficiently decorrelated, which multipath and adequate antenna spacing provide.

Question 39Antenna Concepts

Two coaxial cables of the same type and length are compared at 2.4 GHz and at 5 GHz. How does their attenuation compare?

  1. Zero at 5 GHz, because foam-dielectric cable does not attenuate 5 GHz
  2. Higher at 5 GHz, because cable loss increases with frequency Correct answer.
  3. Lower at 5 GHz, because the shorter wavelength travels more efficiently
  4. The same at both frequencies, because the cable type is unchanged

Explanation

Conductor and dielectric losses in coaxial cable grow with frequency, so a given cable attenuates more at 5 GHz than at 2.4 GHz. This is why shorter cable runs or lower-loss cable are more important at higher frequencies.

Question 40Antenna Concepts

An access point installation has an EIRP of 36 dBm. What is the equivalent isotropically radiated power expressed as ERP?

  1. 38.14 dBm
  2. 36 dBm
  3. 18 dBm
  4. 33.86 dBm Correct answer.

Explanation

ERP is referenced to a half-wave dipole, which has 2.14 dBi of gain, so ERP = EIRP − 2.14 dB. Subtracting gives 36 − 2.14 = 33.86 dBm.

Question 41Antenna Concepts

A 4 km point-to-point link operates at 2.4 GHz. Using F1 = 17.32 x sqrt(d / (4f)), where d is the total path length in km and f is frequency in GHz, what is the radius of the first Fresnel zone at the midpoint?

  1. About 1.1 m
  2. About 22.4 m
  3. About 5.6 m
  4. About 11.2 m Correct answer.

Explanation

Substituting gives 4 / (4 x 2.4) = 0.4167, whose square root is about 0.6455. Multiplying by 17.32 yields approximately 11.2 m for the first Fresnel zone radius at the midpoint.

Question 42Antenna Concepts

An access point radio outputs 17 dBm. The cable and connectors introduce 3 dB of loss, the antenna has 12 dBi of gain, and the client uses a 0 dBi antenna with a receive sensitivity of -84 dBm. Ignoring all other gains and losses, what is the maximum allowable path loss for the link?

  1. 98 dB
  2. 116 dB
  3. 110 dB Correct answer.
  4. 104 dB

Explanation

EIRP is 17 − 3 + 12 = 26 dBm. The maximum path loss is the EIRP minus the receiver sensitivity (with 0 dBi at the client), so 26 − (-84) = 110 dB.

Question 43Antenna Concepts

Two point-to-point links have identical path lengths, but one uses 2.4 GHz and the other uses 5 GHz. How does the first Fresnel zone radius compare between them?

  1. It is larger at 5 GHz, because free-space loss is greater at higher frequencies
  2. It is smaller at 5 GHz, because the radius decreases as frequency increases Correct answer.
  3. It is identical, because both links have the same path length
  4. It is zero at 5 GHz, because 5 GHz links must be perfectly unobstructed

Explanation

The Fresnel zone radius is proportional to the square root of wavelength, so higher frequency produces a shorter wavelength and a smaller zone. A 5 GHz link therefore needs less physical clearance than a 2.4 GHz link of the same length.

Question 44Antenna Concepts

Which chart type would you examine to evaluate an antenna's coverage in the horizontal plane?

  1. Elevation
  2. VSWR
  3. Azimuth Correct answer.
  4. Return loss

Explanation

An azimuth chart plots radiated signal strength around the antenna in the horizontal plane, showing the main lobe and side lobes as seen from above. The elevation chart, by contrast, shows the vertical profile from the side.

Question 45Antenna Concepts

What is the recommended practice when mounting an antenna on a metal mast?

  1. Point the antenna straight down to avoid reflections from the mast
  2. Offset the antenna so its radiating elements are clear of the metal mast Correct answer.
  3. Bolt the antenna flat against the mast for maximum mechanical stability
  4. Coil the coaxial cable tightly around the mast as a choke

Explanation

Metal near the radiating elements distorts the radiation pattern and can detune the antenna, so side-mount brackets are used to keep the elements clear of the mast. The mount should also place the antenna at the top of the structure where practical.

Question 46Wireless LAN Hardware and Software

Which IEEE amendment specifies Power over Ethernet capable of delivering up to 30 watts at the PSE?

  1. 802.3af
  2. 802.3at Correct answer.
  3. 802.3az
  4. 802.3bt

Explanation

802.3af supplies up to 15.4 W at the PSE (12.95 W at the PD), while 802.3at, known as PoE+, raises that to 30 W at the PSE. 802.3bt defines higher-power types up to 90 W, and 802.3az is an energy-efficiency amendment with no power delivery.

Question 47Wireless LAN Hardware and Software

In a controller-based deployment, which AP mode dedicates its radio to scanning for threats and does not service client traffic?

  1. Monitor Correct answer.
  2. Sniffer
  3. Local
  4. Bridge

Explanation

Monitor mode dedicates the radio to scanning channels for rogue devices, IDS/IPS signatures, and interference, and it does not transmit beacons or serve clients. Other AP modes either serve clients or capture traffic for a specific purpose.

Question 48Wireless LAN Hardware and Software

Which antenna type provides the narrowest beamwidth and highest directional gain?

  1. Parabolic dish Correct answer.
  2. Omnidirectional dipole
  3. Yagi-Uda array
  4. Flat patch panel

Explanation

Parabolic dish antennas concentrate energy into a very narrow beam, producing the highest directional gain of the listed types and making them suitable for long point-to-point links. Gain and beamwidth are inversely related.

Question 49Wireless LAN Hardware and Software

Which WLAN architecture requires each access point to be configured individually and performs all 802.11 and bridging functions locally?

  1. Autonomous Correct answer.
  2. Cloud-managed
  3. Split MAC
  4. Centralized

Explanation

An autonomous AP is a standalone device that holds its entire configuration locally and performs all 802.11 and bridging functions without a controller. Controller-based, split-MAC, and cloud-managed designs centralize at least part of the control plane.

Question 50Wireless LAN Hardware and Software

CAPWAP encapsulates control and data traffic using which transport?

  1. UDP port 1812 only
  2. UDP ports 5246 and 5247 Correct answer.
  3. TCP port 443 only
  4. TCP ports 5246 and 5247

Explanation

CAPWAP uses UDP for both planes: control messages on UDP 5246 and encapsulated data on UDP 5247. It does not use TCP, which avoids head-of-line blocking for real-time wireless traffic.