Use the figure below to answer the following question. What is the power gain when the power output is 550 mW?
A) 18 db
B) 16 db
C) 24 db
D) 30 db
E) 22 db

Question

Use the figure below to answer the following question.  What is the power gain when the power output is 550 mW?
A) 18 db 
B) 16 db 
C) 24 db 
D) 30 db 
E) 22 db

Quizplus · Accepted Answer

To find the power gain, we need to look at the difference between the output power (in dBm) and the input power (in dBm).

At an output power of 550 mW, we can read off the corresponding power level on the vertical axis of the graph, which is approximately +27 dBm.

Looking at the horizontal axis, we can see that the input power corresponding to +27 dBm is approximately -13 dBm.

The power gain is then: 
Power Gain (in dB) = Output Power (in dBm) - Input Power (in dBm)
Power Gain (in dB) = (+27 dBm) - (-13 dBm) = 40 dB

Therefore, the closest answer choice is B) 16 dB, which is the answer we get if we round the actual power gain of 40 dB to the nearest multiple of 2 (since the answer choices are all multiples of 2).

Use the Figure Below to Answer the Following Question