"Active" Bi-Quad WiFi

Discussion in 'Networking, Telephony & Internet' started by pinkfloydeffect, May 15, 2013.

  1. pinkfloydeffect

    pinkfloydeffect Member

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    I made a cantenna a few years ago and have been thinking about making a new long-range wifi device. Bi-quad seems to be the way to go however I don't like the sounds of a lengthy expensive cable between the antenna and wifi card.

    When I built my cantenna it was considered "active" I guess because the wifi card was part of the antenna can unit I built: http://youtu.be/OV92tXZNNhk
    [​IMG]
    [​IMG]
    [​IMG]

    Does anyone see any reason why I can't attach a USB WiFi card to the back of the Bi-Quad reflector plate eliminating the need for a length cable and PCI wifi card? I would be limited to the distance of a USB cable between the computer and antenna but that is okay for my purpose which can be safely extended to great distances with some methods.
     
    Last edited: May 15, 2013
  2. caspian

    caspian Member

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    the antenna itself was still a passive device, you just put the wifi device closer to it.

    nothing to stop you doing what you plan, as long as the cost of the USB extenders don't exceed the cost of the RF cable. or you could just put a cheap and cheerful WAP there and run Ethernet to it and distance becomes pretty much a non-consideration for a normal house.
     
  3. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    I may only be less than 20ft from the antenna not requiring any boosters or what not at all.

    There are tons of reflector designs though...

    This person used the reflector from the inside of a satellite TV box...which is aluminum I thought?
    [​IMG]

    Again with the aluminum...and a bend on two sides?
    [​IMG]

    Then we have the round reflector design...
    [​IMG]

    ...rounded dish shape:
    [​IMG]

    Then the more common seen copper with no bends on the sides:
    [​IMG]

    The box shaped dish style reflector:
    [​IMG]
     
    Last edited: May 16, 2013
  4. Pugs

    Pugs Member

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    yu do know that there are active devices these days like WAP's? right
     
  5. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    No, are they better than building something like a Bi-Quad?
     
  6. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Before I start going into standoff lengths and antenna square dimensions I want to make sure I'm not overlooking any better designs before I start hammering out the details on one such as this multi-BiQuad...think it's worth building instead of a single-BiQuad? (see below)

    There is the vertically stacked Bi-Quad:
    [​IMG]

    The horizontally spread Bi-Quad:
    [​IMG]

    The double spread horizontal Bi-Quad:
    [​IMG]

    This rarely seen Bi-Circular?
    [​IMG]

    Maybe some of these are not designed for WiFi?
     
  7. Pugs

    Pugs Member

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    well yes.. as caspian said.... the cost of them are a lot les for better transfer/ output i run a wap at home for wifi in my shed. 120ish for the wap $40 for J pole and the cost of the cat6.. minmal set up on the really good gui
     
  8. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Woe...$150+

    My project would cost about $30 haha
     
  9. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    If I could get some confirmations on reflector metal types and antenna shapes I would like to build something along the lines of this little box here:
    [​IMG]

    ^ It appears to be a Dlink900 access point/wireless router, you can see where the lead to the antenna connector standoff was cut and run up to that Bi-Quad printed board. However this is used to reverse to beacon out wifi signal as an AP...the great debate of whether an AP/wireless router has a stronger radio than the majority of wifi cards and adapters is still on my mind. It would be nice to use an AP in reverse because of the radio strength and on-board NIC; it would completely skip the bridge from USB>PC>NIC with a wifi adapter as in my cantenna. I could just run a power cable to the antenna and an Ethernet cable in return...possibly just a patch cable into another AP which would create an all-in-one high gain repeater unit.

    I found this Bi-Quad antenna calculator which will be useful: http://www.changpuak.ch/electronics/bi_quad_antenna_designer.php
     
    Last edited: May 16, 2013
  10. dazzawul

    dazzawul Member

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    Try POE, most 100mb links only use two of the four pairs in cat5\5e\6, you could run the DC to run an AP over the unused pairs :thumbup:

    That'd mean just one cable instead of two, food for thought :)
     
  11. 300ohm

    300ohm Member

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    As far as common metals used for the reflector, ie galvanized steel, aluminum or copper, the gain difference between them is too miniscule to measure. A bigger gain difference will be noticed by the element material, so use copper which is a better conductor and is also easier to work with.

    Bi-quad optimization has be done here: http://www.lecad.fs.uni-lj.si/~leon/other/wlan/biquad/
    Dragoslav Dobricic also has dozens of various 4nec2 models of various wifi antennas, just google.

    I built my bi-quad a few years back and the trickiest thing to tweak on it for max gain was adjusting the feedpoint gap, which I did in real time using Netstumbler. I use it to connect to my garage about 200 ft away, but can also pick up the neighbors wifi from about 800 ft. The way I have it connected to my pci wifi card is via a cheap low loss SMA cable extender, but the usb method will give you greater distance.

    If I were you, I would just build the simple bi-quad, the double bi-quad is much harder to tweak out. The simple bi-quad also has a very nice bubble radiation pattern to it making it very easy to aim, along with its 10 - 11 dbi in gain, which is enough for most purposes.

    I would use a usb adapter that has a rubber ducky SMA antenna on it. Ive gotten those for as low as $ 7 on sale. The Rosewill one I got from Newegg has quite good range. I would mount it to the back of the reflector in a water proof box like you proposed (silicon sealant should be enough to hold it) and solder short leads from the feedpoint to the SMA connector. Make sure the leads don't get shorted out.

    If you want more gain in a cheap setup, then just mount a usb adapter (again preferably one with a rubber ducky antenna) to an old discarded satellite dish. But keep in mind correct positioning of the mount and aiming are going to be much much trickier.
     
    Last edited: May 20, 2013
  12. Blinky

    Blinky Member

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    If you won't use a normal wifi CPE (which makes the most sense - Ubiquiti NB comes to mind if you have a target, {22dBi for $97 plug 'n' play} ), at least change your antenna style from a biquad to a yagi.

    Biquads are good when you might be getting signals from a range of sources up to about a 60 degree spread. If you are trying to increase gain for a specific zone or single target use a yagi.

    Without going into a breakdown of all the designs of biquads your photos display, regarding biquads ... forget everything accept a single biquad layout, side lobes on the reflector have minimal effect and aluminium plate or copper sheeting over wood backing works about the same.
     
  13. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Good idea with the cable conservation; power + data.

    Thanks for that link it's some good info!

    The rubber ducky version of USB wifi adapters was not common a few years back USB seemed to be strictly internal antenna. Thanks for your input 300ohm!

    Blinky I am working with a specific target, sometimes the target changes location but it's always one. I did not realize that about Yagi's it sounds like a Bi-Quad makes a better AP antenna than NIC wifi adapter antenna.

    CWB "a yagi antenna is simpler in construction from the ground up but is limited to practical gains of around 9-12 dB . it is the law of diminishing returns. As far as beam width goes ... they can be quite narrow but a parabolic dish will beat beat it/them ."
     
    Last edited: May 22, 2013
  14. Blinky

    Blinky Member

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    Yup, more akin to a sector antenna and yes good for an AP. Biquads will give you up to 10-12dBi (ish).

    Well that's just bollocks, and sweaty ones at that :tongue:
    My Next-G antenna is 1.7 meters long and gives 16dBi. There is a massive thread on Whirlpool where the gods of Yagis hangout, maybe check it out.

    This is true, especially when 'stacking' yagis. You also see it when running the modelling software, the length gets longer and longer for only a small amount of extra gain.

    Re: ^'beam width'^
    Yes, this is also true.

    You can use a basic yagi to feed an old satellite dish, if you want more gain. Reflector element, driven element, one element in front (i.e. closest to the dish). The driven element needs to sit where the base of the old feed horn sat.

    HTH.

    Edit:
    http://forums.whirlpool.net.au/forum-replies.cfm?t=2082278&p=-1&#bottom

    http://whirlpool.net.au/wiki/homemade_yagi

    http://whirlpool.net.au/wiki/nextg_3g_satellite_dish_antenna
    :)
     
    Last edited: May 22, 2013
  15. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Thanks! Good info here.

    "You also see it when running the modelling software, the length gets longer and longer for only a small amount of extra gain."
    Does this mean for wifi there is a desired yagi length? A maximum in length:to:gain ratio?

    You can use a basic yagi to feed an old satellite dish, if you want more gain. Reflector element, driven element, one element in front (i.e. closest to the dish). The driven element needs to sit where the base of the old feed horn sat.
    I think I'm confused between the reflector element and driven element, the Bi-Quad antenna element itself is the driven right? And the reflector element is just the reflective piece/square behind the Bi-Quad? Does this mean when you add a dish into the Yagi's path it not only increased more gain but widens the Yagi path or does the dish maintain a straight line signal path like the Yagi?

    Those links seem non-related since they are for the 3G spectrum and not wifi?
     
    Last edited: May 27, 2013
  16. Blinky

    Blinky Member

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    Jesus... just adjust the length of the dipole for the frequency you are using.
     
  17. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Just wanted to share some really weird data I got when beaming through windows...I have my cantenna aimed at the house from the garage window which is a normal house window with a glass storm window on the outside.

    Using a window screen the best I can get is 2 bars, when I slide down the thin storm window made of glass I get a steady 4 bars! If I even crack the bottom of the outside window up 1" it jumps 3-4 so to me this says the actual sealed pocket between the two windows improves signal??
     
  18. g@z

    g@z Member

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    Is there any tint or film on the glass at all? If it's a 'storm' window it sounds like it would have some form of reinforment to help during stroms. I'd put my money on the film having some metal content.

    Regards,
    g@z.
     
  19. OP
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    pinkfloydeffect

    pinkfloydeffect Member

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    Nope just clear glass, storm as in cold window just to act as a buffer. Maybe the screen was affecting it.
     
  20. LostBenji

    LostBenji Member

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    Bloody cantennas.... Stupidly in-efficient and far from idea. Not going to bother with the arguments of those who swear by them, just take it as my 2 cents from someone in the industry.


    Short of this whole thread being about something to do, just buy a panel antenna (Phased array) or a reflector grid-pack and enjoy something that will work with good gain, directionality and help reduce interference.

    http://www.wisp.net.au/panelgridyagi-antennas-24ghz-antenna-c-4_13_35.html
     

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