Difference between 2.4GHz and 5.8Ghz antennas

Discussion in 'General Electronics Chat' started by electronewb, Jan 18, 2015.

  1. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    What are the main differences between a 2.4GHz antenna and a 5GHz antennas? I have a cheap AV wireless Tx & Rx that I bough for dirt cheap it runs on 5GHz but it didn't come with antennas. Both the Tx and Rx have 3 SMA connectors for MIMO antenna setup. Could I just use any type of antennas I have a few 2GHz antennas that I have from an old modem? Also I looked on ebay and they have 5GHz high gain antenna (passive no power required) By high gain do they just mean bigger and longer so it induce more of the signal??? To me they all look the same except the high gain one which are much bigger that the duck tail ones.

    Thanks
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Probably wont work. An antenna used at twice its design frequency goes from current fed to voltage fed or vice versa.

    Gain in an antenna is created by bending the antenna's radiation pattern so more of the energy goes in the direction you need it to go; and less goes where you dont need it. For that to happen, the antenna must be physically larger than it would otherwise be.
     
  3. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    Can you explain the "bending the antenna radiation pattern?
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    A simple vertical monopole antenna produces an equal distribution of energy in azimuth (radiates equally well toward all points of the compass). Adding a second vertical monopole spaced between ~0.15 and 0.4 wavelength parallel from the first, and then feeding both monopoles with equal currents, but with the correct phase shift between the currents, will cause the pattern to become cardtiod shaped, where more energy radiates in the preferred direction, and much less in the opposite direction. The power input to the antenna hasn't changed, but the field intensity in some directions has... e.g. the FM station that serves a large metropolitan area from a mountain top that is not in the middle of town. It "wastes" signal transmitted away from town, so would prefer to send all of its output toward town.

    A similar effect happens when you lengthen a 1/4 wavelength monopole (operated against the required ground plane) to odd multiples of 1/4 wavelength, except that power gain is equal in all directions. This is called an Colinear array. The added energy that is radiated at low angles above the horizontal comes from not radiating as much energy at high angles of radiation and even straight up. Rarely is it beneficial to send energy upwards at more than 10 degrees above the horizon. For example, the FM station again. Very few of its listeners are in airplanes or out in space...
     
    Last edited: Jan 18, 2015
    electronewb likes this.
  5. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    Thanks for the explanation I find antennas are such simple design but it's so fascinating to understand what's involved and what they can do!!

    [​IMG]
    In my case I was thinking to get one of those like the picture above at the receive end but I have 3 SMA sockets on my unit and that dish take one coax N type connector Would I need an antenna combiner?



    [​IMG]


    Also would or 3 of those side by side to create an array would work I think those small antennas take SMA, so one antenna per SMA connector?






    [​IMG]

    At the transmit end I was thinking of getting 3 of those (above) 5.8GHz 7dBi Gain






    Also is there a way to boost the overall signal on top of using directional antennas and higher gain antennas? Is there anything on the market like an antenna booster? My unit is only 150mW


    Thanks
     
  6. electronewb

    Thread Starter Member

    Apr 24, 2012
    260
    3
    Just one more thing!!!!! I just found the frequency range that the units operate it's 5.15~5.25GHz band Would any 5GHz antennas work or I have to be specific to 5.15~5.25GHz range? I looked online and they are pretty rare in tat specific range.

    Thanks
     
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