Juniper Exam JN0-251 Topic 12 Question 30 Discussion

According to the Wikipedia article on dBm1, a 10 dB increase in level is equivalent to a ten-fold increase in power, and a 10 dB decrease in level is equivalent to a ten-fold decrease in power. Therefore, a 3 dB change in level is approximately equivalent to doubling or halving the power.

In this scenario, the signal strength has changed from -70 dBm to -73 dBm, which is a 3 dB decrease in level. This means that the signal strength has halved, or decreased by 50%. To calculate the ratio of the signal strengths, we can use the following formula:

fracP1P2=10fracx1x210

where P1 and P2 are the powers in mW, and x1 and x2 are the levels in dBm. Plugging in the values from the scenario, we get:

fracP1P2=10frac70(73)10=10frac310approx1.995

This means that the power at -70 dBm is about 2 times higher than the power at -73 dBm, or equivalently, the power at -73 dBm is about 0.5 times lower than the power at -70 dBm.