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Thread: WiFi Roof-rack

  1. #1
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    WiFi Roof-rack

    I know there are many links to sites which sell 2.4Ghz 802.x antennas but I am at a loss as to which I can mount horizontally across my roof-rack of my car or inside the trunk, i would prefer if the antenna is "tube" like. Any suggestions? Oh yea just to be perfectly clear, it needs to be Omni Directional.
    2003 Subaru Impreza TS
    Staus: Done.. too lazy to make pictures lol.

  2. #2
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    If you mount an omni horizontally, you will have very limited range, as omni antennas are vertically polarized with a horizontal beam eminating 360 degrees with a virtical beam width of approximately 25-30 degrees.

    Without getting too technical, you will basically have great range directly to the left and right of the vehicle, but not forward and in back of the car. If you mount it running across the car, you will have coverage to the front and read, but not the sides. I would recommend instead you buy one of the low profile ceiling mount style antenna (usually about 3.5dbi gain) and mount it in the center of you rack on the roof of the vehicle so you will have 360 degree coverage, and about a 35-45 degree verticle beam width as well.


    Hope this helps

  3. #3
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    Hypothetically could I somehow link 2 omnis that are rotated 90 deg to each other and hook them into the same network card?
    2003 Subaru Impreza TS
    Staus: Done.. too lazy to make pictures lol.

  4. #4
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    You could, but a 2.4ghz duplexer is not cheap. You can expect to spend about $150 for a quality one. If you are willing to spend the money, I would get a 1 watt amplifier, some quality connectors, a nice weather resistant ceiling mount omni (you can airbrush it to match your paint) and use the shortest cables possible. This will usually put your EIRP at the legal limits, and greatly increase your effective range.

  5. #5
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    Thanks, Im not sure i want to spend that kind of money. Anyways as far as a low profile mount is this what you were talking about? http://www.hyperlinktech.com/web/hg2414p.php

    What kind of coverage/range would that give?

    Just for reference is this the kind of omni I would use for connecting 2 together?

    http://www.hyperlinktech.com/web/hg2415u_pro.php

    Also where do i get a duplexer and 1w amp for this purpose?

    Thanks again.
    2003 Subaru Impreza TS
    Staus: Done.. too lazy to make pictures lol.

  6. #6
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    As far as the omni, you pulled up a direcctional patch antenna, try this link http://www.hyperlinktech.com/web/hg2403cu.php

    As far as a duplexer, it is also refered to as a splitter or signal combiner. Here is a link http://www.hyperlinktech.com/web/sig..._2400_2way.php but remember you will loose about 2-3.5 dbi every time you split the signal, not to mention with those antennas you linked to, you need to have at least 6 feet of separation for diversity, or you will have high data error rates. Also, at those prices, you could definately afford an amp. http://www.hyperlinktech.com/web/ha2401dx_agc.php is a good example of a quality 1 watt amp, which can be often had for about 260 from other vendors.


    Let me know if you need any technical details or additional information

  7. #7
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    What kind of range will that 3db ceiling mount give me?
    2003 Subaru Impreza TS
    Staus: Done.. too lazy to make pictures lol.

  8. #8
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    for every 3dbi you increas your power, you double the range of your equipment. (Logarithmic scale) Take the output power of your device in mw, calculate your line and connector loss, add in any amplifiers you may have, then add your antenna in. Take the final falue and convert it to db, which you can then get an approximate range from.

    Examples (Depends on your surroundings)

    30mw ~150-200 ft
    100mw ~ 300-350 ft
    500mw ~ 850-1000+ ft
    1 watt ~ 1500+ ft

  9. #9
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    Last question... I think. Thanks for all the help by the way.

    Would I be able to attach this to that antenna?
    http://www.linksys.com/products/prod...id=36&prid=578

    The Hyperlink antenna says it has a "Integral N Type Female" Connector, I have no idea what that looks like. Im guessing thats not the same as the little plug you find when you can detach the antenna from a card.
    2003 Subaru Impreza TS
    Staus: Done.. too lazy to make pictures lol.

  10. #10
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    What kind of PC are you putting this into, do you have an open PCI slot, if so I would reccomend this http://www.netgate.com/NL2511.html and add a PCMCIA to PCI adapter. It has a higher trasmit power which will give you much better range.

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