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Exam 350-401 topic 1 question 854 discussion

Actual exam question from Cisco's 350-401

Question #: 854
Topic #: 1

An engineer measures the Wi-Fi coverage at a customer site The RSSI values are recorded as follows:

• Location A: -72 dBm
• Location B: -75 dBm
• Location C -65 dBm
• Location D -80 dBm

Which two statements does the engineer use to explain these values to the customer? (Choose two.)

A. The signal strength at location C is too weak to support web surfing
B. Location D has the strongest RF signal strength
C. The RF signal strength at location B is 50% weaker than location A
D. The RF signal strength at location C is 10 times stronger than location B
E. The signal strength at location B is 10 dB better than location C

Show Suggested Answer

Suggested Answer: CD 🗳️

by JackDRipper at Nov. 6, 2023, 6:39 a.m.

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Horsefeathers

Highly Voted 1 year, 6 months ago

Selected Answer: CD

The following matches options C & D perfectly: "For every 3 dB decrease, the power is cut in half. Similarly, every 10 dB increase in level is 10 times the power, and every 10 dB decrease in level results in 1/10 the power. This is sometimes referred to as the “rule of 3s and 10s.”" https://www.sciencedirect.com/topics/computer-science/signal-strength

upvoted 8 times

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kaupz

Highly Voted 1 year, 6 months ago

Selected Answer: CD

C and D(is the closest correct) Because rule of 10 and 3s

upvoted 8 times

kaupz

1 year, 6 months ago

A)-65dBm is enough for web browsing) - wrong https://community.cisco.com/t5/wireless-mobility-knowledge-base/snr-rssi-eirp-and-free-space-path-loss/ta-p/3128478#:~:text=The%20closer%20this%20value%20to,on%20power%20levels%20and%20design. "Typically voice networks require a -65dBm or better signal level while a data network needs -80dBm or better. Normal range in a network would be -45dBm to -87dBm depending on power levels and design" B) the closer the value to + side, the better the signal - wrong

upvoted 2 times

kaupz

1 year, 6 months ago

C) -75dBm is 3dBm weaker than -72dBm, so this divides the coverage with 2 (50% less) D) imagine 2squaremeters equals -80dBm, then if each time the RSSI gets better 3dBm then the the x squaremeters get multiplied with 2. -80dBm = 2sqm -77dBm = 4sqm -74dBm = 8sqm -71dBm = 16sqm -68dBm = 32sqm -65dBm = 64sqm this means not only it is just 10 times stronger, but 32 times. D) Yet again, the closer the value to + side, the better the signal, not the other way around - wrong

upvoted 2 times

kaupz

1 year, 6 months ago

oops - E) Yet again, the closer the value to + side, the better the signal, not the other way around - wrong

upvoted 2 times

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chmacnp

Most Recent 4 months, 3 weeks ago

Selected Answer: CD

C & D - the answer is very clearly not A (-65dBm is considered fair and adequate for surfing), B (D is the weakest not the strongest, & E (the signal strength is 10dB worse than C) leaving option C + D as only viable options

upvoted 1 times

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cjoyce1980

8 months, 2 weeks ago

Selected Answer: CD

The two correct statements based on the RSSI values are: D. The RF signal strength at location C is 10 times stronger than location B This is because a 10 dB difference in RSSI corresponds to a tenfold increase in signal strength. The difference between Location C (-65 dBm) and Location B (-75 dBm) is 10 dB, meaning the signal at Location C is 10 times stronger. C. The RF signal strength at location B is 50% weaker than location A A 3 dB difference corresponds to approximately half the signal strength. The difference between Location B (-75 dBm) and Location A (-72 dBm) is 3 dB, which suggests that the signal strength at Location B is about 50% weaker than at Location A. Explanations for incorrect options: A: The signal strength at -65 dBm (Location C) is typically sufficient for basic web browsing, so this statement is incorrect. B: Location D has the weakest signal strength at -80 dBm, not the strongest, making this statement incorrect. E: The signal strength at Location B is not better than Location C; in fact, it is worse by 10 dB.

upvoted 2 times

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chiacche

9 months, 2 weeks ago

Selected Answer: CD

-3 dBm --> x1/2 +10 dBm --> x10

upvoted 1 times

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Nickita

1 year, 3 months ago

Selected Answer: AB

I'd go for A and B because read carefully - the mission is to explain it to a customer! A customer is non technical most probably and will see these equations as bullshit...

upvoted 1 times

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