signal strength explanation

[kenperez87]

Could I please have a human, simple, straight-forward explanation of why a signal strength is written/read like "-85DBm"?  Why negative?

Thanks in advanced!

-Kenny

[Rasika Nayanajith]

Reference value  dBm corresponds 1mW(so 0dBm=1mW). So if you get any power level more than 1mW, it has to be +dBm, where as if you get less than 1mW power level, it has to be -dBm value.

Remember that power level (in mW) increase/decreate x10 times mean +/-10dB. If power level double/half, it is +/-3dB

1W       = 30dBm

100mW= 20dBm

10mW = 10dBm

1mW   =  0 dBm

0.1mW = -10dBm

0.01mW = -20dBm

0.001mW= -30dBm

HTH

Rasika

*** pls rate all useful responses ***

[kenperez87]

thanks for taking the time to answer, so the question is still open... why when you are talking about signal strength on access points one can find a doc stating that using x HZ of signal strength you  get -85DBm... wath does it mean?

-Kenny

[kenperez87]

Also, to the @CommunityModerator .... I dont know who did it, but I will appreciate if the question is marked as answered once I (person who asked the question) consider the question has been answered as I know most of the times, other people wont look at questions that show as answered and therefore I dont get the feedback I wish to get.

thanks...