• Is there a list of errata for the new CWAP-402 book?

    There is a mistake on page 383.  The definition of signal to noise ratio is backwards.

    SNR = signal strength value in dBm - noise floor value in dBm.  In the example the calculation is

    25dB signal to noise ratio= (-70dBm signal ) - (-95dBm noise)

    More information can be found at



  • David,

    I don't have a copy of the book.  What is the definition in the book ?

    The example, and answer, you give is correct.

  • Hi Howard,

    Yes, the numeric calculation is correct but a different part of the page needs another look.

    There is the text on page 383, "Technically, SNR is defined as the difference between the noise floor and the signal of interest in dB.  The formula for calculating SNR for RF networks is simple: 

    SNR = noise floor value in dBm - signal strength value in dBm."

    This reversal in the formula is also repeated in the exam moment paragraph further down the page.


  • Yep.That gives you the wrong sign for the SNR.

  • Thank you for reporting this. It will be added to the errata when it is published.


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