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Wireless Networking Communications Hardware

4km WiFi Range w/ $5 DIY Antenna 254

Mignon writes "This industrious fellow in New Zealand made his own WiFi antenna using a USB WiFi adapter and a Chinese 'spider skimmer mesh scoop.' He got about 17 dB signal improvement for about US $5 in materials." Update: 05/25 23:09 GMT by T : Reader John Stockdale offers a U.S. hosted mirror of the site. Update: 05/26 13:58 GMT by T : Reader Jared Mauch contributes another mirror.
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4km WiFi Range w/ $5 DIY Antenna

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  • by os2fan ( 254461 ) on Tuesday May 25, 2004 @06:59PM (#9253841) Homepage
    All he needs now is a signal to pick up. {laugh - it's funny}
    • by Anonymous Coward
      Someone sent up us the Slashdotting
    • I know the parent's a joke, and I laughed :), but NZ does have a reasonably active wireless community [].

      I go on the occasional wardrive across parts of NZ and we get around one hundred up to two hundred APs on relatively short trips (which they usually are).
    • One word... (Score:5, Interesting)

      by B747SP ( 179471 ) <> on Tuesday May 25, 2004 @08:50PM (#9254725)


      I already built one of these things after the site first surfaced a couple of weeks ago. The neat thing about it is that it's modular insofar as your choice of radio goes. Unplug the 802.11b tranceiver, replace it with a usb Bluetooth tranceiver, aim at the nearest bus stop, and wa-la, bluejack city. Want to use 802.11g, or heaven forbid, 802.11a, plug one in! It's the ultimate in modular l33+ hax0r radio toys. Why, I reckon you could even plug an usb IrDA adaptor in there...

      No, wait... :-)

  • What direction? (Score:3, Informative)

    by kdougherty ( 772195 ) on Tuesday May 25, 2004 @07:00PM (#9253851)
    If it was omni-directional, then I'll be very impressed, but you can make a pringles antenna for very cheap, and get about 10 miles range (line of sight).
    • Re:What direction? (Score:3, Informative)

      by kdougherty ( 772195 )
      You can also make an antenna out of an old tin can, which is very cool and very cheap for all those interested in an effective method for long range. ml
    • Re:What direction? (Score:3, Informative)

      by sbranden ( 471243 )
      You have to take the cost of the wifi card, pigtail and cable into account. This system is much cheaper because they are not required. It just uses a usb cable (less loss and cheaper than coax), a usb wifi device and a reflector.
      • Re:What direction? (Score:3, Informative)

        by lullabud ( 679893 )
        USB has even better than less loss, it has effectively no loss, since it's not an analog signal and has error checking between the WiFi card and the host controller. This definitely sounds like a cheaper, more efficient solution. Maybe when a mirror is up I'll actually get to see it!
    • Re:What direction? (Score:5, Informative)

      by another_henry ( 570767 ) <slashdot@henryhallam . c j b . n et> on Tuesday May 25, 2004 @07:07PM (#9253918) Homepage
      It couldn't possibly be omnidirectional. That would break the laws of physics. To get a boost in signal strength you must either make it more directional or increase the power itself with an amplifier.
    • by j1m+5n0w ( 749199 ) on Tuesday May 25, 2004 @07:16PM (#9254014) Homepage Journal

      The super cantenna [] is only 12 db. 17 is more impressive, and should result in greater range.

      Range itself is hard to compare, as it depends on environment, the radios used (cheap 35 mW? 200 mW with good receive sensitivity?), whether the same antenna is used on both ends, and the subjective evaluation of what exactly constitutes a "useable signal".


      • I was wondering why your post was informative rather than funny until I checked the link. The original Cantenna (Heathkit?) was a paint can filled with transformer oil and a 50 ohm resistor dummy load for tuning transmitters--not much gain there! :^)
      • 5 dB of additional gain at one end will give you 77% more range, all other things being equal. Adding 5dB at EACH end, and you have tripled the distance

        Or, it can give you a nice punch through vegetation loss

        Does anybody have reliable (or empirically determined) Eb/N0 and NF figures for popular WiFi hardware, for doing real link budgets?

        • You can find transmit power / recieve sensitivity numbers for a lot of prism2 cards here []. I suspect most of these numbers are gleaned from product brochures, so you mileage may vary.


          • Interesting table, although lacking in meat.

            A receiver sensitivity number, without specifying test conditions, is really meaningless. Vendor A could specify a signal of -80 dBm for a BER of 10**-6, while vendor B could specify -90dBm for a BER of 10**-3. Without both numbers, a purchaser cannot make an informed decision. (This is all moot if there is a standard published test condition, perhaps as part of the 802.11 standard, which I should read, but that smacks of RTFA)

            Wbat I would love to see is Eb/

      • the funny part is most of these people waste a GOB of their Rf power in the feedline.

        I can take the worst pringles can antenna and stick it almost directly on the Wifi card (1 1/4 wavelength of feedline) and beat the best home made antenna with 10 feet or more feedline and 3 connectors because of the card connector and adapter to the N feedline connector...

        losing a gob of power in the feedline and connectors (almost 1 db per connector is lost at 2.4ghz)

        removing losses adds up to greater radiated power fa
      • Making your own Cantenna [] is pretty easy too.
    • I'm convinced that Pringles can antennas are an uban myth. First up, the cans are made of cardboard, and aren't reflective. Second, they're the wrong size for 2.4GHz. All you actually get is a mismatched-for-size flat metal plate that will offer some vague semblance of directionality, but if anything, a pringles 'can' is going to work as an attenuator, not a waveguide.

      Still, placebos work on a substantial portion of folks, so if you feel that your pringles can antenna works for you, far be it from me to te

      • Umm, Pringles cans are coated internally with an aluminium paint so they ARE reflective. Btw the origional source for most people hearing about Pringles antenna's was this [] PBS article.
      • Urban myth? Look here []. 12dB gain is hardly an urban myth.

        The difference between your speculations and reality is that "Pringles cantennas" simply use the Pringles can as a housing for a "shotgun" Yagi antenna. Anything which relies solely on the Pringles can will do a whole lot of nothing, but it's possible to use several different varieties of ordinary cans (Pringles, beef soup, etc) to house a good antenna.

        While it's certainly better for anyone just looking for gain without any hassle to get a premanuf

      • The inside of pringles cans are aluminized, thus reflective.
  • freecache link (Score:5, Informative)

    by rpdillon ( 715137 ) * on Tuesday May 25, 2004 @07:01PM (#9253857) Homepage
    There was a story about freecache, but no one here on slashdot ever uses it in stories. Here's a pre-cached link, in case the main NZ server goes up in smoke.
  • by Marxist Hacker 42 ( 638312 ) <> on Tuesday May 25, 2004 @07:01PM (#9253859) Homepage Journal
    Still, impressive gain for $5 worth of parts. Makes me wonder what I'll get if I can ever find the right connector for my Linksys wireless router to hook it up to standard coax and a pizza dish I took out of a dumpster.
    • by B747SP ( 179471 ) <> on Tuesday May 25, 2004 @09:10PM (#9254883)
      As I said already, I built one of these already. My shopping list ran to a bit more than $5.00 though....

      • One 13 inch (the biggest one they had, basically!!!) Dumpling scoop thing from the 'Thai Kee' (chinese, not Thai!) supermarket on level 1 on the Market City shopping centre in Sydney's (Australia) chinatown. Turn right when you enter the shop, they're at the far end of the right-most aisle - AUD$15.85
      • One Netgear MA111 USB/802.11b adaptor from Dan at - AUD$69.00
      • One plastic hose joiner thing from Bunnings Hardware (Bunnings == direct copy of Home Depot) - AUD$0.80
      • One adhesive band-aid strip, to cover the gouge I put in my finger trying to cut the hose joiner up the side - AUD$0.00 (stolen from the office medical cabinet)

      I didn't shop around for best price, etc, etc, 'cos I knew that once this thing hit slashdot, there was gonna be a worldwide stockout on the chinese cookware. I could have gotten things a bit cheaper if I had shopped around, but short of an AUD$1200+ aeroplane ticket to Guangzhou and buying direct from manufacturers, there was no way this setup would cost $5.00 of anyone's money. With time and petrol and driving around, I guess it cost AUD$100.00. Good fun tho, and worth every cent.

  • by Sialagogue ( 246874 ) <> on Tuesday May 25, 2004 @07:02PM (#9253868)
    General Tso's Access Point.
  • by I_Love_Pocky! ( 751171 ) on Tuesday May 25, 2004 @07:02PM (#9253872)
    it has other uses as well. If you wrap your head in this spider silk mesh it is even more effective at blocking the evil thought control waves than tin foil!
  • by bobhagopian ( 681765 ) on Tuesday May 25, 2004 @07:02PM (#9253877)
    I wonder if there are hidden shortcomings to this technique. If it only costs $5, I would think that manufacturers of wireless access points would have implemented this a long time ago (or at least made it available as a $40 add on). After all, there *is* a market for it, and at least some people would buy such a device.
    • by Carnildo ( 712617 ) on Tuesday May 25, 2004 @07:05PM (#9253905) Homepage Journal
      I wonder if there are hidden shortcomings to this technique. If it only costs $5, I would think that manufacturers of wireless access points would have implemented this a long time ago (or at least made it available as a $40 add on).

      The most likely shortcoming is that it probably violates the FCC rules about how much power an unlicensed transmitter can put out.
      • by Tony Hoyle ( 11698 ) <> on Tuesday May 25, 2004 @07:17PM (#9254020) Homepage
        Possibly not.

        In the US I believe the output is measured by the effective output of the antenna (essentially transmitter power + gain AFAIK). This allows you to build directional antennas that can go some distance (you're also allowed a whole 1W signal which is quite a lot).

        OTOH in Europe we measure EIRP, which is total power in any direction - so directional transmitters are illegal (we also only get 100mw to play with). This is why things like the WRT54G are so useful - you can have a really powerful receiver (not limited) and a still use the legal transmitter in the other aerial.

        • by j1m+5n0w ( 749199 ) on Tuesday May 25, 2004 @07:36PM (#9254182) Homepage Journal

          IIRC, the maximum tx power in the 2.4ghz band for unlicensed users is 1 watt, or 4 watts EIRP. For point-to-point links, though, you can trade 1db of power reduction for 3 db of antenna gain, allowing much higher EIRP.

          More info is here []


        • I don't believe directionals are illegal.. there are still rules for how to deal wiht it.. it's just not as liberal as in the US.

          Generally it's something like 3db of gain is permitted for each 1db drop in transmitter power.

          So you can't just start throwing directionals off your 100mW transmitter.. you also have to attenuate it properly first.

          This allows you to get directional gains, but keeps a sane limit on the total power.

    • It is directional, so it isn't especially suited to laptops and base stations--for those you want something omnidirectional, so that I don't need to know where the base station is and keep my antenna stationary relative to it.
  • Ok, did anyone grab content before it went up in smoke?
  • Death by /. (Score:2, Funny)

    by gphinch ( 722686 )
    How much does the antena cost that increases your site bandwidth?
  • by osewa77 ( 603622 ) <> on Tuesday May 25, 2004 @07:03PM (#9253891) Homepage
    This site [] shows what's commercially available, but gives no price. Does any fellow slashdotter have a clue about exactly how much money has been saved?
    distract free online advertising []
    • Try looking at hyperlink [], superpass [], and netnimble [] for comparison.


    • by CaptBubba ( 696284 ) on Tuesday May 25, 2004 @07:30PM (#9254138)
      Here is a nice list [] of directional antennas. They aren't exactly exmensive if you are willing to go with an ugly reflector grid model. 15dBi for $40 and 19dBi for $45.

      Also, to those confused about how antenna gain works. The gain is measured in comparison to the output of an isotropic radiator, basically something that puts out the same signal strength in all directions. So that means that any unamped antenna with a gain higher than 1dBi is directional in some sense, because the total radiated power is still the same. So-called omnidirectional antennas really are only omnidirectional in the horizontal plane, if you go up or down their signal strength drops off rapidly.

      • So that means that any unamped antenna with a gain higher than 1dBi is directional in some sense, because the total radiated power is still the same.

        No, +1dB gain is still gain.
        I'm pretty certain that 0dB == unity gain.
        It's a logarithmic scale, with negative dBs for attenuation situations. log(1) = 0
      • This may seem redundant, but could you find an antenna with a relatively narrow scope and use it in wardriving to try and triangulate the source based on signal strength? Obviously this is a yes if you are within the designed range of what you are detecting, for arguments sake, 2Km, but could you communicate with a network 4km away if only your antenna was suped up?

        I am sure someone has written an app to detect incomming signal strength almost akin to passive sonar, but would you actually be able to create

  • by pedantic bore ( 740196 ) on Tuesday May 25, 2004 @07:05PM (#9253911)
    The antenna is directional so this kind of range isn't that helpful unless the two end points are stationary. Which is exactly the kind of thing I don't use wireless for...

    I guess it's a neat hack if that's the only way to communicate with your friend 4Km away, and you only have one friend (or your one friend has a nice network connection to the rest of the world and is willing to share).

    • Iguess it's a neat hack if that's the only way to communicate with your friend 4Km away, and you only have one friend (or your one friend has a nice network connection to the rest of the world and is willing to share).

      An acquantance of mine is considering setting up something like this, since he can't get high-speed internet access -- too far for DSL, and the cable company hasn't upgraded his section of the network yet. However, a five-mile wireless link would let him work off someone else's high-speed c
      • If it's just a matter of finding someone to help, please, help me out here.

        I'm trying to do this with a friend that's 3 miles away. thing is, we don't have LoS. There's mostly trees between us but even if we stand on each others houses I doubt we have a clear line of sight.

        Do you know what the options are? I can't exactly mount a 20' tower on the roof.
      • I'm getting ready to do something like this for my fiance... our houses are only 5 miles apart, and no desire to set her up with DSL and the associated contract since she'll be moving in here in a few months anyhow. Tie this into my DSL here, then point a pringle's can at her house, then her laptop with a wi-fi card can piggy-back onto my connection
    • What, you mean like Athens Metropolitan Network? []
      Very cool i would say...
      At take a look at the node count []
      To these people it's very usefull.
    • But, you need line of sight? I'm trying to do exactly that, connect to my friends network. If we got 2mbit, we'd be happy. We live three miles apart.

      But this whole line of sight thing. How are you supposed to do that? It's not like there's a grassy field between us. There's harldy a building though, it's all trees, but if you need LoS you'd need a very tall tower to mount this thing on regardless?

      I'm trying to find a way to get this done without a LoS. It doesn't have to be 802.11, we just
      • A friend of mine just solved the exact same problem. Only a 1/2 mile separation, but trees and hills intervened. He purchased a WISP bridging setup, I'm guessing it's this [] one. He said it has a 12 mile range, and does not require line of sight.

        I hope you have $2K laying around...

    • by Hamstaus ( 586402 ) on Tuesday May 25, 2004 @07:43PM (#9254228) Homepage
      The antenna is directional so this kind of range isn't that helpful unless the two end points are stationary.

      Wrong. It isn't helpful unless one end point is stationary. Which is a big difference.

      Case in point. I live on a fairly large property. I'm trying to extend my wireless signal to the edge of the property, where my hammock is, so I can work in my hammock. A directional antenna hooked to the transmitter on my router inside my house extends the range in whatever direction I point the antenna in, i.e. towards my hammock. Since the antenna increase pickup as well as transmit power, I just put it on my stationary router, and I don't need to do anything to my wi-fi card on my mobile laptop.

      If I wanted to extend coverage to the whole property, I could aim my antenna at a distant repeater to get omnidirectional coverage from the repeater, while still increasing range from my base-station router.

      Wireless rules.
      • Yes, but you're planning ahead. Imagine that you walk out, across your fairly large property, and when you get to your hammock you decide that it really would be nicer to work down by the lake (or anywhere other than in the hammock). You have to hike back to the base station, decide where you want to be, aim the antenna in that direction, and then walk back again. Every time you change your location, you need to make another trip home. Since we're talking about a 4Km range, that could be a lot of walkin
    • Not true. My connection to home is currently wireless with a directional antenna. DSL only works over high quality phone lines. I've always wonder just how much copper is there between my house and the phone company... All place in the ground at a large labor expense.

      Wireless power delivery doesn't work so well (though Tesla fans might try to claim otherwise if they don't understand exactly what his assumptions were). For most data uses though, wireless makes perfect sense.

  • by jstockdale ( 258118 ) * on Tuesday May 25, 2004 @07:08PM (#9253935) Homepage Journal []

    Mirrored as much as I could of the images before the server was smoked.

    -S ...
  • Nice work (Score:5, Insightful)

    by Beuno ( 740018 ) <`argentina' `at' `'> on Tuesday May 25, 2004 @07:09PM (#9253942) Homepage
    Good to know some people are still trying to improve technology remembering that not everybody has 1 trilion dollars a month to spend on over-priced gadgets.

    Good work!
  • by ( 778374 ) on Tuesday May 25, 2004 @07:10PM (#9253957) Homepage

    Piece of number eight wire reputation.

    Hmm, now I feel sadly parochial.

  • by Anonymous Coward on Tuesday May 25, 2004 @07:13PM (#9253983)
    In theory for a transmitting antenna, there is no limit to how much gain you can get. Gain is the ratio of received power to the power you would get with an isotropic radiator. To get gain, you just focus the beam tighter. The limit to how tight you can focus the beam is set by the aperture of the antenna. The gain of a receiving antenna is set by its effective area. Gain isn't hard to get.

    The bigger problem is to get line of sight. At this frequency, if you can't get line of sight, all the gain in the world won't help.
    • I've been having trouble getting an exact definition of Line of Sight. This means you have to actually be able to SEE the remote side with nothing in the way at all? I don't know how useful a 10km range is if you need that type of LoS.

      See, I'm trying to get a wireless connection to my friends network about three miles away, directly. We can't erect 100' towers so we're trying to figure out our options. We can mount the things on our roofs but we won't have direct line of sight (some trees, the curve
      • I believe in this case Line of Sight just means you need to point it at the transmitter, you don't actually have to see it.
        • Unfortunately, Line of Sight means a direct line from the transmitter to the receiver, with nothing in the way. Trees and vegetation really attenuate the signal, and buildings are almost impossible to get through with basic off-the-shelf wireless equipment. Some people have problems just getting a signal through to their basement.
          • Not only do you need to be able to see the receiver for line-of-site, but you actually need to have a sort of cigar or sausage-shape area, with the diameter at the center being measured in meters, with no obstructions. That is, merely being able to spot the receiver through the gap between a couple of tree branches won't do.
  • by kaan ( 88626 ) on Tuesday May 25, 2004 @07:13PM (#9253984)
    I lived in Wellington, New Zealand for a while, and I sure hope this guy is using this to steal access from somebody else, not to share his bandwidth with other people. Internet connectivity was very expensive down there, and metered (we had dsl through Telstra). Even the much-hyped CityLink wireless service is pay-as-you-go. But with his $5 setup, this guy can scan around his neighborhood until he finds somebody with an open network, and presto! Free 'net access.
  • Just think what one could do with an EMP blast (electro-magnetic pulse) discharged in the focal point of the chinese spider mesh thing.
    (just kidding)
  • One word (Score:5, Funny)

    by azav ( 469988 ) on Tuesday May 25, 2004 @07:32PM (#9254159) Homepage Journal
    "Chinese parabolic cookware"

    OMFG is that funny.

  • by timothy ( 36799 ) on Tuesday May 25, 2004 @07:34PM (#9254175) Journal
    I just took a long car trip, relying mostly on (purchased and municipally provided*) 802.11 access, and in preparation for that trip bought a highish-end 802.11 card and extrernal patch antenna, which indeed came in handy.

    I considered one of the USB 802.11 donglers, but passed on account of ignorance: Are any of them of Linux-friendly? Are some brands better than others? Can anyone provide reception figures or anecdotes?

    It certainly would be nice to have a rooftop mount on my station wagon to which I could as necessary string up a 15' USB cable and thumb-drive-style 802.11 thing :)


    *Thanks, taxpayers and politicians of Salt Lake City!
  • He got about 17 dB signal improvement for about US $5 in materials.

    I will finally get a good connection from the living room!
  • by Cthefuture ( 665326 ) on Tuesday May 25, 2004 @07:44PM (#9254233)
    Of course different areas have different rules, but just about everywhere there are restrictions on antenna gain and power for 802.11. Especially if you are not a licensed amateur radio operator.

    These things are unlicensed part 15 devices which have strict restrictions on power output (which includes any gain from directional antennas) and can not interfere with licensed devices like amateur radio operators.

    I'll leave it up to the reader to Google for what the limits are in your area since it varies. Just remember that you can't just slap on any super-high-gain antenna and remain legal.
  • by eggboard ( 315140 ) * on Tuesday May 25, 2004 @07:48PM (#9254262) Homepage
    Not political dangers, not legal dangers, but health risks. This is an unshielded piece of metal that's surely producing signal all over the place. Wi-Fi is microwave radiation. While it's not a big deal for the tiny antennas in cards or bigger antennas that are found on access points, when you start boosting the gain and have directional focus, it's critical for your long-term well being to not spend extended periods of time (or, for higher-gain antennas, any time whatsoever) in the "blast" of the beam. There are well-documented health risks from microwave radiation exposure but only at high levels and short distances.

    Because this ad hoc device hasn't been checked out in any fashion, it's possible that even with it facing away from you, you could be subjecting yourself to cellular damage from the microwave radiation. I wouldn't recommend this. The cantenna design is much simpler and safer. Other ad hoc designs at least have parameters that prevent so much signal spew. This one worries me.
    • The device is putting out the radiation... No matter antenna you put on it you don't increase the output of the device. Now you do focus it into a much "hotter" spot when you make it directional. Even so though none of these devices are allowed to excede 1W of effective radiated power (No commercial consumer device currently excedes 250mw).

      To give you an example... You microwave uses 4000 times that much power to cook food with.

      I would imagine if you stood in the beam path of a 20+db antenna for a couple months you would have health issues... but you also wouldn't have a signal :}

      As health risks go a cell phone is a MUCH larger output of power and you stick it right next to your head. Worry about those first :}

      And FWIW cantennas are no better... most directional antennas send most of their power out the front but all of them have sidelobes.
  • that is:
    2.385 miles (4km)
  • by HaeMaker ( 221642 ) on Tuesday May 25, 2004 @08:00PM (#9254369) Homepage
    If he is getting that kind of gain from the scooper, imagine if he used the wok...

  • That this guy kept the other $145 he saved from building his own antenna because he's definitely gonna need it to pay his web host.
    I have the site saved, so anyone want to host a mirror, let me know..
  • Once you've connected to the network, you'll just need to connect again in an hour or two.
  • by nurb432 ( 527695 ) on Tuesday May 25, 2004 @08:56PM (#9254778) Homepage Journal
    Since old dishes are about free, how about replacing the LNA with one of those same sort of external wifi transceivers?

    Anyone try such a thing?
  • Would an old satellite dish work for this? I notice that DirecTV dishes are quite shallow, so would this be a problem.

    You can get a used DirecTV dish pretty cheap.
  • by po8 ( 187055 ) on Wednesday May 26, 2004 @12:49AM (#9256102)

    As cool as this antenna is, it isn't very expensive to buy a nice prebuilt wireless antenna these days. Pacific Wireless dishes [], for example, are about US$50 for 19dBi or $70 for 24dBi. I've used their products, and they are very nice. I've given up on building 802.11 antennas: it's too much work vs the cheap commercial antennas for me.

I just asked myself... what would John DeLorean do? -- Raoul Duke