• I feel a bit dumb for asking this question, but it isn't explained in the book, it simply states that it is true.

    I'll take a short reason or a link providing a detailed one. ;)


  • in order to carry information, certain characteristics of the RF wave have to be changed. Remember about binary, it is either zero or one. If there is no change, then no information will be carried. Frequency is one of the characteristic of RF wave that can be changed. Amplitude and Phase is another

  • Is this covered in detail on any of the other exams?

  • the detail wouldnt be covered in the exm i believe. It is not required for you to know in-depth of the physical property of the signal. I just know more since i have an RF engineering background.

  • I mean any of the exams,CWAP or CWNE?

  • /usr Escribi?3:

    I feel a bit dumb for asking this question, but it isn't explained in the book, it simply states that it is true.

    This statement comes out of the field of information theory. If you're worried about taking the CWNA exam, don't stress too much about this issue. Information theory is pretty much out of the scope of the exam. Sometimes, in the study guide, I tried to put in background information that I thought would be helpful in broadening or deepening the reader's understanding of the topic, even if the information was not specifically going to be covered on the exam. I guess the flip-side of that decision is that readers might assume that they need to know 100% about everything in the book, which isn't true. Suffice it to say that everything you need to know to pass the test should be in the study guide, but there's some extra stuff in there too. I hope that's more helpful than it is harmful...

    To answer your question: in order to convey information, some quality of the signal has to change. Think about an alphabet where you only had one letter; could you make any words? As we know from binary representation, if you have at least two letters ('1' and '0'), then you can represent anything else that you want, but you can't do it with one letter because nothing can change.

    In RF, we have an electromagnetic waveform. It has two basic qualities: amplitude and frequency. Wavelength is just another way of expressing frequency, and phase is derived from frequency as well. So, in order to convey information with an RF signal, you have to change the amplitude, the frequency/wavelength, or the phase. Which one changes depends on the encoding method used. In amplitude modulation (AM), you change the amplitude while leaving the frequency constant. In frequency modulation (FM), you change the frequency while leaving the amplitude constant. In phase modulation, you change the phase (which, in a way, is like changin the frequency, but in a way, it's not) while leaving the amplitude constant. And in quadrature amplitude modulation (QAM), you change both the phase and the amplitude.

    Hope this helps...

  • Joshua, how is your dad Joe doing? Is he still at 802 connect?

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