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Electromagnetic Waves: Frequency Bands

  1. Jul 11, 2013 #1
    Hello everyone. I'm studying wireless communications at school, and I have a question... If frequency is the amount in time that something oscillates, in this case, electrons, wouldn't a higher hertz, mean faster data transfer? A 2.4 MHZ way is must slower than a 2.4 Ghz wave correct? So wouldn't putting wireless communications like routers and Access Points, in the higher ranges mean better throughput?

    Also how are these waves measured? I see many sites saying microwaves are very small, hence the name, but how does one go about measuring a wave's size?
     
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  3. Jul 11, 2013 #2

    nsaspook

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    There is a difference between the 'carrier' frequency and the modulation frequency (the speed of changes to that carrier) but in general as the carrier frequency increases more bandwidth is available to be used for data (limited by the need for other channels near the carrier frequency). The actual throughput is a product of the modulation frequency and the bit efficiency rate per modulation frequency cycle. I've actually used leased satellite transponders to send Morse Code and sent live video using HF links below 10mhz so the actual modulation technology can sometimes be more important than the carrier frequency in determining data throughput.

    Microwave band wavelengths are usually calculated with a simple formula:
    http://www.photonics.byu.edu/fwnomograph.phtml
     
    Last edited: Jul 11, 2013
  4. Jul 11, 2013 #3
    The modulation can take numerous compression forms as well, for example in radios. You have numerous protocols. 1 main category of the digital side is the FSK frequency shift key modulation. This protocol has 4 modulation levels that ride the carrier frequency along with the privacy tones or color code in digital. The IP format also has a variety of protocols IPv4, IPv6 etc

    In the ethernet however this corresponds to the number of bits per packet.
     
  5. Jul 11, 2013 #4

    davenn

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    they (RF signals) are measured using frequency counters
    My trusty ol' HP5343A that I have at home goes from 10 Hz up to 26GHz
    its one of my treasured bits of test gear

    attachment.php?attachmentid=60218&stc=1&d=1373593093.gif

    Dave
     

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  6. Jul 12, 2013 #5

    Baluncore

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    You can measure the wavelength with a light globe. The traditional way to measure wavelength was to couple the signal to two parallel bare wires. Keep the far end open circuit. The transmitted wave will reflect of the open end and travel back to the source. As it does, interference will take place between the two waves which will create standing waves on the two wire line. You can find the voltage nulls of the standing wave by sliding a light globe along touching the parallel wires and looking for the positions where there is no voltage to light the globe. Those points will be half a wavelength apart. The method works with a shorted line also.
     
  7. Jul 12, 2013 #6

    davenn

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    yup the good old Lecher lines
    gosh its been years since I have done wavelength measurement and calc's that way :)

    Dave
     
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