4km WiFi Range w/ $5 DIY Antenna

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.

Comments

Just need a signal

[os2fan]

All he needs now is a signal to pick up. {laugh - it's funny}

What direction?

[kdougherty]

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?

[kdougherty]

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. http://www.turnpoint.net/wireless/cantennahowto.ht ml

Re:What direction?

[sbranden]

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?

[another_henry]

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.

Re:What direction?

[Anonymous Coward]

It could be omni in the H plane with a seriously pinched E plane (think gain antennas for 2m or 70cm)

Re:What direction?

[lullabud]

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?

[j1m 5n0w]

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.

"Omnidirectional" is somewhat of a misnomer. Omnis transmit a pancake-shaped signal -- good signal in all directions in the same plane, but very little signal up and down. What you're refering to is called an isotropic radiator.

-jim

Re:What direction?

[Daemonik CyCow]

Why can't we break the laws of physics?

Re:What direction?

[j1m 5n0w]

The absolute power limit is 1 watt for unlicensed 2.4 ghz equipment. The EIRP limit is 4 watts for point-to-multipoint, but can be higher for point-to-point. (Disclaimer: I'm not an RF engineer, so read the actual fcc regulations before you try it.)

more information

-jim

Re:What direction?

[neonsam]

I asked the same question in junior high science...Actually I asked "What happens if you break a law of physics?" His answer - you become very famous.

freecache link

[rpdillon]

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. http://www.freecache.org/http://www.usbwifi.orcon. net.nz/

Re:freecache link

[JonLatane]

Could that be because it's designed for 5+MB files, and there aren't many HTML pages that are that size? Don't waste their bandwidth (besides, the server is down anyway, before it was even cached).

Re:freecache link

[rpdillon]

Actually, I cached it before the story ran because I saw it before it went public (subscriber), but the problem is, if the server goes up in smoke, freecache will stop serving because it can't verify the server is still there. That was my mistake. We need to use freecache in the actual story, rather than in comments, I guess.

Good point about the file size - html != >5MB.

Re:freecache link

[0x20]

...And the Google cache as well

Re:freecache link

[PhrostyMcByte]

It could be because freecache only caches a single file, not anything it links to. Images still come from the original site.

Already slashdotted?

[Marxist Hacker 42]

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.

So now we call it. . .

[Sialagogue]

General Tso's Access Point.

Apparently...

[I_Love_Pocky!]

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!

Why haven't AP manufacturers tried this?

[bobhagopian]

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.

Re:Why haven't AP manufacturers tried this?

[Carnildo]

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.

Re:Why haven't AP manufacturers tried this?

[Tony Hoyle]

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.

Re:Why haven't AP manufacturers tried this?

[j1m 5n0w]

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

-jim

Re:Why haven't AP manufacturers tried this?

[mindstrm]

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.

Death by /.

[gphinch]

How much does the antena cost that increases your site bandwidth?

How Much Do the Commercial Versions Cost?

[osewa77]

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

Re:How Much Do the Commercial Versions Cost?

[j1m 5n0w]

Try looking at hyperlink, superpass, and netnimble for comparison.

-jim

Re:How Much Do the Commercial Versions Cost?

[CaptBubba]

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.

Re:How Much Do the Commercial Versions Cost?

[BattyMan]

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

Too bad it's directional

[pedantic bore]

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).

Re:Too bad it's directional

[Carnildo]

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 connection -- it's just a matter of finding someone willing to help.

Re:Too bad it's directional

[arcanumas]

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.

Re:Too bad it's directional

[Hamstaus]

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.

Temporary Mirror at Stanford University

[jstockdale]

http://www.stanford.edu/~jstockdl/tmp/usbwifi.orco n.net.nz/

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

-S ...

Nice work

[Beuno]

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!

See Kiwis, we really do deserve our...

[interpretthis.org]

Piece of number eight wire reputation.

Hmm, now I feel sadly parochial.

Unlimited gain! (but it doesn't matter)

[Anonymous Coward]

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.

must be for a user, not a provider

[kaan]

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.

We get signal

[Anonymous Coward]

Someone sent up us the Slashdotting

comparing apples to oranges

[j1m 5n0w]

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".

-jim

Re:comparing apples to oranges

[AndroidCat]

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! :^)

Re:comparing apples to oranges

[YankeeInExile]

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?

Re:Apple's had this for years

[wankledot]

wtf are you talking about?

The airport base station doesn't have a range anywhere NEAR 14km. There are lots of antenna out there for lots of base stations (including the Airport ones) that will give you that range, but Apple has not "had this for years" any more than every other vendor that sells products with the option of adding an antenna.

Hell, Cisco has products that have 25 MILE ranges, with the right antenna.

Re:Google Cache

[wo1verin3]

I'm only learning html, sorry

How long have you been learning that you haven't gotten to 'hyperlink' yet?

One word

[azav]

"Chinese parabolic cookware"

OMFG is that funny.

USB 802.11 dongles -- are any Linux friendly?

[timothy]

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 :)

timothy

*Thanks, taxpayers and politicians of Salt Lake City!

Re:USB 802.11 dongles -- are any Linux friendly?

[slandis]

I use a Netgar MA111 USB wireless key in my Linux router. You need linux-wlan-ng, which provides the proper usb_prism2 drivers (and of course, working usb hardware).

Works pretty dang well, probably better than the Windows setup.

Re:USB 802.11 dongles -- are any Linux friendly?

[lakeland]

I've got one based on the atmel (at76c503_rfmd). It works pretty well. My only gripe is that even though it is open source, it isn't currently in the kernel so I have to recompile before every kernel upgrade.

I've been using it to access my server at home because I'm too lazy to lay cable under the house.

Shut up! Apple rules. Period.

[Anonymous Coward]

Yes it does. I've been accessing my Apple base station sitting in my apartment in San Fran from where I work in Oakland for YEARS now. In fact, I even access my base station from AIRPLANES while flying overhead!!!! Apple is THAT GOOD! Obviously you don't use Apple so you wouldn't understand. So SHUT UP.

Please be aware of the regulations

[Cthefuture]

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.

Dangers of this kind of ad hoc device

[eggboard]

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.

Re:Dangers of this kind of ad hoc device

[Gaewyn L Knight]

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.

Re:Dangers of this kind of ad hoc device

[jandrese]

No commercial consumer device currently excedes 250mw

What about those nutty 300mW Reliawave cards? Heck, they even sell access points with 15dBi omnis builtin.

Re:Dangers of this kind of ad hoc device

[afidel]

We had a really high gain 4 pannel style antenna at Cisco's wireless division and I can tell you that when that thing was being fed at 100mW that standing in front of it would warm you up. The radiated power was around 8W so it probably wasn't life threatening but I can tell you that I wasn't about to stand in front of it to find out.

Shouda used the Wok...

[HaeMaker]

If he is getting that kind of gain from the scooper, imagine if he used the wok...

I seriously hope...

[swaic]

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..

One problem with Chinese cookware antennas...

[teamhasnoi]

Once you've connected to the network, you'll just need to connect again in an hour or two.

One word...

[B747SP]

Bluejack

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... :-)

usb + dish network dish?

[nurb432]

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?

Kind of...

[mindstrm]

Snipped from some site:

The FCC regulations for Point to Multi-Point allows only 36 dBm (4 watts) EIRP. This is 30 dBm (1 watt) into a 6 dBi antenna. If you use a 10 dBi wireless antenna, you must limit your transmitter (or amplifier) to 26 dBm (10 + 26 = 36 dBm). For a 14 dBi panel wireless antenna, this allows a 22 dBm transmitter (or amplifier).

According to FCC regulations, 2.4 GHz Part 15.247 point-to-point transmitters may use a 30 dBm transmitter with a 6 dBi antenna. For a 3 dB increase in antenna gain, the transmitter power output must be reduced by 1 dB.

My comments below:

In Canada:
The maximum EIRP is 4 Watts for both point-to-point and multi-point networks with a maximum of 1 watt from the transmitter.

Meaning:

In the US, Point to point links have a distinct advantage.

It's not $5.00, even in your money...

[B747SP]

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 http://www.usbtech.com.au/ - 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.

How About an Old Satellite Dish

[JMcJames]

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.

Re:Shut up! Apple rules. Period.

[pi42]

Actually, a lot of products have really long ranges -- right out of the box! I got a Linksys WiFi router and it seems like I can pick up my SSID "linksys" network all over the place!

Heh heh..

Little brain seeks big brain.

[WinterpegCanuck]

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 a two way connection?

Because Scotty said so...

[pelrun]

"Ye cannae change the laws of physics, laws of physics, laws of physics. Ye cannae change the laws of physics, laws of physics, Jim."

And who are we to argue? :)

vs commercial antennas

[po8]

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.

Re:So what's to stop you...

[lommer]

There's nothing stopping you (if you leave out the legal), but it wouldn't be all that useful. While an amplifier would boost your output, it will do nearly nothing to increase the signal that you recieve i.e. you will be speaking louder but the person talking to you will still be speaking at the same volume. You may well ask then how an antenna's gain works out overall then, as you are still basically just boosting the wattage of your signal, not the other guy's. The answer there comes from the directionality of the antenna - while the other guy isn't speaking any louder the directional antenna allows you to filter out the noise coming from everywhere else, making it easier to hear what he's saying. Thus with a directional antenna, you're getting two good effects, while with the amp you're really only getting one. Now, OTOH, if you stuck an amp on your rig AND the other guy's rig, then you'd be talking :-)

Hey I know that guy...

[OrangeNZ]

I can't believe it! I work at the chain (DSE - dse.co.nz) that the mentioned WiFi adaptor came from (It's a Zydas that we rebrand).. In fact, I work at the branch on Vivian St, Wellington where Stan (one of the guys involved) actually bought those.. One of our best customers.

Never thought I'd see something local on /. :)

Three Words

[warlockgs]

Yan Can LAN!