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 is the effect of increasing antenna height on a point-to-point outdoor wireless link?
Answer: Reduces ground reflection and improves LOS clearance
Raising antenna height reduces ground-level obstructions, clears Fresnel zones, and minimizes ground reflection interference on point-to-point links.
In RF propagation, what is 'near-far problem'?
Answer: High-power nearby stations overwhelming receivers trying to hear distant weaker stations
The near-far problem occurs when a high-power close transmitter overwhelms the receiver, making it unable to decode signals from more distant, lower-power transmitters.
Which propagation model is commonly used to estimate path loss in urban outdoor cellular and Wi-Fi environments?
Answer: Okumura-Hata model
The Okumura-Hata model is widely used for predicting path loss in urban environments based on frequency, distance, and antenna heights.
When a 2.4 GHz signal passes through a human body, approximately how much attenuation should be expected?
Answer: 3–5 dB
The human body causes roughly 3–5 dB of RF attenuation at 2.4 GHz due to the water content absorbing microwave-frequency energy.
What is the primary purpose of a link budget calculation in wireless network design?
Answer: Verifying that sufficient signal margin exists over the entire RF path
A link budget accounts for all gains and losses across an RF path to confirm the received signal exceeds the receiver's sensitivity by an adequate margin.
Which type of fading is caused by rapid fluctuations in signal amplitude as a receiver moves through areas of constructive and destructive multipath interference?
Answer: Rayleigh fading (small-scale fading)
Rayleigh fading describes rapid small-scale amplitude variations caused by the vector summation of multiple reflected, diffracted, and scattered signal components.
In the context of 802.11ax (Wi-Fi 6), which feature specifically improves efficiency in dense multipath environments by dividing a channel into narrow orthogonal subcarriers?
Answer: OFDMA
OFDMA (Orthogonal Frequency Division Multiple Access) subdivides a channel into resource units with narrow subcarriers that are orthogonal, improving spectral efficiency in multipath-rich environments.