What is "dbm" numbers?

Question

Level 1

5 points

What is "dbm" numbers?

I want to check my iPhone for the "more accurate" reception reading. Well, I got it now what do I do with it? The smaller the number the better the reception it appears, but why are they negative numbers?!? What do the numbers stand for?
Can anyone help me understand what these number mean? Please and Thank you.

iPhone 3G 2.0.2, Windows Vista

Posted on Sep 1, 2008 5:44 PM

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Answer 1

Sep 1, 2008 5:55 PM in response to dragonzmajic

<http://en.wikipedia.org/wiki/DBm>
If you climb a cell-phone tower and hold your phone near the antenna, you might get a positive reading. Inside a microwave oven would be about +60 (don't try this with your iPhone).

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Answer 2

NR2D

Level 1

56 points

Sep 2, 2008 6:53 PM in response to Malcolm Rayfield

dBm is a transmitter (and received signal) power level. The higher the number, -30 dBm vrs. -60 dBm the better. If you increase your power by 3 dBm, -70 dBm to -67 dBm, theoretically you have doubled your power.

To get technical it is a power level expressed in decibels reference, above (+dBM) or below (-dBm) 1 milliwatt of power. 1 milliwatt of power is 1 thousandth (10 to the -3, if I could have used a superscript I would have) of a watt.

Rich Dunklee
NR2D

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