# Forum

## Decibel Normalization - RF Math

4 posts by 3 authors in: Forums > CWNA - Enterprise Wi-Fi Admin
Last Post: June 30, 2005:
• In the CWNA study guide, in the section on dBm, 10's and 3's are used differently. Here's what I mean. There's an example something like this:

1 mW = 0 dBm

Now that we?¡é?€??ve done this, we can determine how many dBm would equal 300 milliwatts:

1 mW x 10 x 10 x 3 = 300 mW
1 mW +10 dB + 10 dB + 3 dB = 300 mW
1 mW + 23 dB
300 mW = 23 dBm

Normally, 1 mW + 10 db + 10 dB + 3 dB = 200 mW, but here it is said to equal 300 milliwatts. Nowhere in the study guide is this clearly explained and I want to make sure my conclusion is correct.

Is it, therefore, correct to say that Decibel Normalization refers to the fact that we use the 10's and 3's as their normal math representation or is the book wrong.

Tom Carpenter

• I think the 300 is a typo, I was confused as well.

• Hi sysedco:

Please let me know if the errata list does not cover this one.

http://cwnp.com/products/errata.html

I hope this helps. Thanks. /criss

• The errata does indeed deal with it - wish I had known this a few weeks ago, it would have saved me lots of brain injury <smile>. It's too bad this concept is not explained better in the study guide. There is a sample given, but it doesn't really give details about why we're doing things the way we are.

Thanks for the help.

-Tom

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