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Thread: Antenna

  1. #1
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    Default Antenna

    Hey all

    Im not too good with antenna terms and forgive my ignorance but does anyone know of any good omni directional antennas with a good beam width and good RX and TX for an alfa 500mw? Ive searched the forum but its more theory discussions as opposed to actual products.

  2. #2

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    omni directional antennas with a good beam width and good RX and TX
    The beam width of an omni directional antenna is 360 degrees. TX power and RX sensitivity are controlled by the card itself and not the antenna. You are looking for Antenna Gain, expressed in dB.

    I suggest you at least read THIS to gain a better understanding of what an antenna does.

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    Thanks for the link. From what I have read getting a better antenna increases range but it doesn't mean you will receive any transmission.

    I have found 2 antennas:

    10dBi gain - Beam width h plane is 360 - Bean width e plane is 30.

    7dBi gain - Beam width h plane is 360 - Bean width e plane is 40.

    Should I go for the 7dBi or 10dBi?

  4. #4

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    Depends on what you want to do with the antenna. If you are more concerned with transmitting than receiving (ie. the distance to your AP is farther), you should probably choose neither and look for a good directional antenna. If you are concerned with general receive capability (ie. wardriving), then based on the 2 choices, I would go with the 7dBi. Although some may disagree, and usually 10dBi is better than 7, out of the 2 choices you have provided, the 7dBi only has 1.5 VSWR where the 10dBi has 2 VSWR. In my opinion, any gain in capability of the 10dBi over the 7dBi is lost due to the greater VSWR of the 10.

    But, you may want to hold off on the "buy button" and see if any other members have a differing opinon or idea...there are others on this forum who seem to be much more knowledgable about antennas than I.

    Also, make sure the antenna will fit your wireless card. The more adapters and cable you need, the greater the loss in signal quality.

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    Thanks for the insight, appreciate it. I have found another one:

    http://www.faculty-x.net/9dbi-sma.htm

    Its 9dBi and has a VSWR of < 1.5:1

    A quick question, is the vertical beam width an important factor when considering an omni directional antenna? The other products posted above had 30degrees and 40degrees accordingly whereas this one has 25degrees.

  6. #6
    My life is this forum Barry's Avatar
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    Quote Originally Posted by BlackMat View Post
    Thanks for the insight, appreciate it. I have found another one:

    http://www.faculty-x.net/9dbi-sma.htm

    Its 9dBi and has a VSWR of < 1.5:1

    A quick question, is the vertical beam width an important factor when considering an omni directional antenna? The other products posted above had 30degrees and 40degrees accordingly whereas this one has 25degrees.
    This might help you. Think of an omni antenna's signal area as a doughnut. The antenna being in the hole in the middle. The higher the dB the flatter and farther out the area will be. I usually wardrive with either a 3 or a 7 dBi antenna. It depends on what kind of areas I'm going to be in. For wide open single story areas, like ca-chunk neighborhoods I use the 7dBi antenna for range. If I'm going to be in town with multi-story buildings I use the 3dBi antenna to "see" stuff on the 2nd and 3rd story. So to close, a 3dBi antenna will look like a doughnut, shorter horizontal range, but more vertical reach. That 9dBi antenna will look more like a flat washer, more horizontal range, but a very narrow vertical reach.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

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    Aha, excellent analogy Barry. I will be in relatively open areas and in multi story buildings too. Just my thoughts but the 7 dBi sounds like the ideal purchase when taking all the factors into account although 9 dBi would be nice too.

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    My life is this forum Barry's Avatar
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    Quote Originally Posted by BlackMat View Post
    Aha, excellent analogy Barry. I will be in relatively open areas and in multi story buildings too. Just my thoughts but the 7 dBi sounds like the ideal purchase when taking all the factors into account although 9 dBi would be nice too.
    Antennas are relatively cheap. All my antenna mounts are rp-tnc, even the one on my eeePc, so my linksys 3dBi stock antennas work on it. Wal-Mart had a blow out sale of the 7bDi linksys antennas once and I picked up a half dozen of them. I don't have anything bigger than the 7dBi antennas unless you count my homemade biquad and primestar directional antenna.
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

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    Senior Member streaker69's Avatar
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    Quote Originally Posted by Barry View Post
    Antennas are relatively cheap. All my antenna mounts are rp-tnc, even the one on my eeePc, so my linksys 3dBi stock antennas work on it. Wal-Mart had a blow out sale of the 7bDi linksys antennas once and I picked up a half dozen of them. I don't have anything bigger than the 7dBi antennas unless you count my homemade biquad and primestar directional antenna.
    You should post a pic of your modified eeePc.

    Did anything ever get published from that guy that took at pic of it at Shmoocon?
    A third party security audit is the IT equivalent of a colonoscopy. It's long, intrusive, very uncomfortable, and when it's done, you'll have seen things you really didn't want to see, and you'll never forget that you've had one.

  10. #10
    My life is this forum Barry's Avatar
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    Quote Originally Posted by streaker69 View Post
    You should post a pic of your modified eeePc.

    Did anything ever get published from that guy that took at pic of it at Shmoocon?
    No, Darren took a pic of it, but it never made it up on their site or forums. I need to finish my usb port mod first, I've also stickerfied the shit out of it...
    Of course, if you really wanted to have some fun, go to Wal-Mart late at night and ask the greeter if they could help you find trashbags, roll of carpet, rope, quicklime, clorox and a shovel. See if they give you any strange looks. --Streaker69

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