RF Behavior & Signal Propagation Flashcards
7 cards from real CWS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 RF Behavior & Signal Propagation flashcards as text
What antenna characteristic defines the angular spread over which the antenna radiates at least half its maximum power (-3 dB points)?
Answer: Half-power beamwidth (HPBW)
The half-power beamwidth (HPBW) is the angle between the two -3 dB points on the antenna's radiation pattern, defining the main beam coverage area.
Which RF propagation effect is responsible for ghosting or shadowing behind large buildings or hills that block a direct signal path?
Answer: RF shadowing (blockage)
RF shadowing occurs when large solid objects block the direct propagation path, creating a 'shadow' zone with significantly reduced signal levels.
A wireless engineer notices a 20 dB signal attenuation after a coaxial cable run. If the transmitter outputs 30 dBm, what is the power at the antenna connector?
Answer: 10 dBm
Power at the antenna connector = transmit power - cable loss = 30 dBm - 20 dB = 10 dBm.
What happens to RF signal propagation when antenna polarization between transmitter and receiver is mismatched by 90 degrees?
Answer: Polarization mismatch loss of approximately 20 dB or more occurs
A 90-degree polarization mismatch between transmit and receive antennas causes severe polarization isolation loss, typically 20 dB or greater.
Which 802.11 feature allows a client to determine the optimal transmit rate by dynamically adjusting MCS based on current channel conditions?
Answer: Dynamic rate shifting (DRS)
Dynamic rate shifting allows devices to automatically select the highest MCS (modulation and coding scheme) that channel conditions can support for reliable communication.
In an outdoor point-to-point microwave link, what is the recommended minimum Fresnel zone clearance percentage to avoid significant diffraction loss?
Answer: 60%
Industry standards recommend clearing at least 60% of the first Fresnel zone to minimize diffraction-related signal loss on point-to-point links.
What is the key difference between Rician fading and Rayleigh fading in wireless channel modeling?
Answer: Rician fading includes a dominant line-of-sight component while Rayleigh fading assumes no dominant path
Rician fading models channels with a dominant LOS component plus scattered paths, while Rayleigh fading models environments with no dominant path and only scattered multipath components.