CWNA-109 · Question #98
As you prepare for a site survey in a multi-floor corporate office, you have learned about several wireless devices that support connection-oriented, real-time applications. These applications are…
The correct answer is A. Microwave ovens C. Elevator shafts. Microwave ovens (A) are a well-known source of RF interference because they operate in the 2.4 GHz range - the same frequency band used by 802.11b/g/n Wi-Fi - and when active, they emit enough energy to cause significant packet loss and retransmissions that real-time…
Question
As you prepare for a site survey in a multi-floor corporate office, you have learned about several wireless devices that support connection-oriented, real-time applications. These applications are sensitive to service interruptions and require excellent signal quality, low latency, and low loss. For that reason, it is important to identify sources of RF interference as well as building characteristics that would cause RF blockage or dead spots. What systems or environmental characteristics are most likely to cause interference or RF blockage and disrupt service for these applications? (Choose 2)
Options
- AMicrowave ovens
- BNarrow hallways
- CElevator shafts
- DRFID chokepoints
- EWorkspace dividers
How the community answered
(25 responses)- A76% (19)
- B8% (2)
- D12% (3)
- E4% (1)
Explanation
Microwave ovens (A) are a well-known source of RF interference because they operate in the 2.4 GHz range - the same frequency band used by 802.11b/g/n Wi-Fi - and when active, they emit enough energy to cause significant packet loss and retransmissions that real-time, connection-oriented applications simply cannot tolerate. Elevator shafts (C) are constructed of steel and metal, making them act like Faraday cages that block RF signals almost entirely, creating reliable dead zones that disrupt wireless coverage for floors and areas surrounding the shaft.
Narrow hallways (B) may create some multipath effects but do not significantly block or interfere with RF signals - radio waves pass through walls and travel around corners. RFID chokepoints (D) use frequencies (typically 900 MHz or 13.56 MHz) that don't meaningfully overlap with Wi-Fi bands, so they aren't a notable interference source. Workspace dividers (E) are made of fabric, wood, or thin partitioning material, which attenuate signals only slightly and don't create dead spots.
Memory tip: Think "M-E-T-A-L" - Microwave ovens radiate RF energy, and Elevator shafts are solid metal enclosures. Both involve metal or metal-band overlap, and both actively destroy signal quality for sensitive applications.
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