問題文
A school has set an access point radio to a transmit power of 17 dBm. The administrator needs the same value in milliwatts to compare it against a regulatory limit stated in milliwatts. Using the rules of 10 and 3 what is the result?
選択肢
- Start from the reference of 20 dBm which equals 100 mW and then subtract 3 dB to halve the power of the radio down to exactly 50 mW.
- The figure of 17 dBm equals 17 mW because dBm counts milliwatts on a linear scale of its own design.
- Start from the reference of 10 dBm which equals 10 mW and then add 7 dB as a factor of seven to reach 70 mW.
- Start from the reference of 20 dBm which equals 100 mW and then subtract 3 dB to remove three tenths of the power for a result of 70 mW.