# Forum

## CWNA Book RF Math Mistake?

3 posts by 2 authors in: Forums > CWNA - Enterprise Wi-Fi Admin
Last Post: July 25, 2006:
• I just started going through the CWNA Book, and I noticed something in the RF Math section on pg 57. I think it might be a mistake, but I just want to see if it is a mistake or something I'm just missing (probably the latter).

On pg 57 they convert 30mW to 13dBm through the following.

1mW *10 *3 = 30mW
1mW +10dB +3dB = 30mW
1mW +13 dB = 30mW

The problem I see is bold. Going by the "rule of 10s and 3s" wouldn't +3dB be expressed as a multiplication of 2 and not 3? so shouldn't 13dB be:

1mW +13dB = ??mW
1mW +10dB +3dB = ??mW
1mW *10 *2 = 20mW

Please let me know if I'm missing something or if this is a mistake.
Thank you,
Kyle

• By (Deleted User)

Have you checked the errata file for this book at
http://www.cwnp.com/cart/products/errata.html ?

• Yep, it's in there. Thank you for the link, I didn't know this existed, but what a great tool!

Thank you

(for anybody else wondering the same... yes, it is a mistake)

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