DefCon WiFi Distance Competition Calls For Entrants

ASLRulz writes "The Adversarial Science Laboratory is running the Wi-Fi Shootout this year at DefCon and we are inviting people to come out and try to beat last years record of 35 miles. Register here. Hope to see you there."

Comments

Homebrew

[Detritus]

Now I know what to do with the surplus 20kW S-band klystron that I have sitting in the garage. All I need is a portable power supply.

Re:Homebrew

[pe1rxq]

A klystron is a type of vaccum tube used to generate microwave signals. Good ones can generate very powerfull signals (plenty-o-kilowatts)

Jeroen

Re:Homebrew

[Technician]

haven't the slightest clue what that mean,

Do a Google search for klystron.

You will find it's a vacuum tube. It has a cavity and is used like a magnitron to create microwaves. On most of them, the cavity contains metal bellows. This enables tuning it over a small range. Small ones were used for tuning the local oscillator in radar sets in the receiver. Tuning a 20,000 watt one to the WiFi band could not only disrupt the competition by jamming the band, but could overload and cook much of the low power stuff in the area.

Maybe he wants to DOS the contest.

To win the contest, he needs to establish a 2 way link. He can't win by blasting a one way signal.

Re:Homebrew

[carnivore302]

Actually, a Klystron is a microwave generator.

A klystron looks and works something like an organ pipe.
In an organ pipe:

Blowing into the organ pipe produces a flow of air.

Flowing air excites vibrations in the cavity of the whistle.

The vibrations flow into the surrounding air as sound waves.

In a klystron:

The electron gun produces a flow of electrons.

The bunching cavities regulate the speed of the electrons so that they arrive in bunches at the output cavity.

The bunches of electrons excite microwaves in the output cavity of the klystron.

The microwaves flow into the waveguide , which transports them to the accelerator.

The electrons are absorbed in the beam stop.

Click here for the Mystery Futures Link!

To be immediately followed by chinese food...

[Ammishdave]

Now all the slashdotters will pull out their favorite cooking utensils

Passive Relaying?

[nacturation]

I assume the "no active relaying" prohibition means that someone can't have waypoint stations to pick up and rebroadcast the signal to the destination. So this leaves the competition open to passive relaying.

How well does the 2.4GHz spectrum interfere with power lines? Would it be possible to put up a structure so that it modulates the power signal which is then decoded on the other end in a similar setup? At the very least, it might win a "Most Creative Bending of the Rules" award or something. :)

35 miles?!

[flopsy mopsalon]

That must be one big-ass pringles container. They get that at Costco or something?

Not necessarily power limited

[elgatozorbas]

Because WIFI operates in the microwave territory, you need a line of sight (LOS). These waves do not go 'around the bend', as e.g. long wave radio does. 'Around the bend' also implies 'around the Earth'. I can imagine that at some point the winners of this contest will no longer be limited by power, but by finding suitable high places to transmit and receive from.

Z

Re:Not necessarily power limited

[elgatozorbas]

More specifically:
D=sqrt(2Rh), with D the distance to the horizon, R the earth radius and h the antenna height. Apparently, the maximum antenna height is '200 hundred feet'. Let's assume this is 200, which equals about 60m (we really use the metric system). The earth radius is 6378km. This implies that the distance to the horizon is about 27km, and the total distance (from each antenna to the horizon) is 54km or 34 miles. Please correct me when I'm making a mistake in these calculations (which may very well be).
Taking into account roundoff errors etc, good luck trying to beat last year's 35 miles...

Z

Other records

[john_smith_45678]

A page to collect 'long shots' (sorted by distance). The goal is not (only) to break records, but also to get a feeling of what can be done with what.

* 82 miles, Utah, using parabolas and amplification (1500 mW) [WWW]Slashdot 10dec2003, [WWW]Rob Flickenger's blog, [WWW]experiment's site
* 116 km (72 miles), California, using parabolas and amplification ([WWW]Computer World, [WWW]HPWREN)
* 110 km in Poland ([WWW]Slashdot23sep2003), the [WWW]polish article (one of the [WWW]translations)
* 70.5 km, Spain, using parabolas ([WWW]CanariaWireless.net)
* 61.1 km, Downtown Seattle to MtBaldi using 24dBi parabolics, no amps (SeattleWireless)
* 35.2196 miles, Nevada, USA, using home built horn ([WWW]Defcon Wi-fi Shootout)
* 52km, Melbourne (Victoria, Australia) [WWW]http://melbourne.wireless.org.au using 25dBi grid pack to 180 degree slotted waveguide.
* 48 km, Perth (Western Australia), using a [WWW]satellite dish with biquad feed, connecting to a 180 degree waveguide
* 45.0 km, TacomaNode to MtBaldi using a 14.5dBi yagi and a 24dBi parabolic, no amps (SeattleWireless)
* 42.0 km, [WWW]Netherlands, SMC-Senao, 2 * 24 dBi dishes (SNR 17 dB)
* 36.4 km, Belgium, using a SlottedWaveguide, a [WWW]Yagi and a parabola ([WWW]Florenville-Arlon)
* 33.7 km (20.9 miles), California, using parabolas ([WWW]Oreilly)
* 26.4 km , Perth (UK) using 10 dBi omni + Parabola 24 dBi (http://www.consume.net/mhonarc/thenet/msg02844.ht ml)
* 24 km, Lausanne/Switzerland, using 2 Paraolic 24 dBi by [WWW]Submusic Team [WWW]photos and explications (in french)
* 10 miles (TestingTenMileLink)
* 15 km, Belgium, using a SlottedWaveguide and a CardboardHorn ([WWW]LouvainWaterloo)
* 9.5 km, Belgium, using 2 CardboardHorn ([WWW]Liege20020615)
* 5 km, Belgium using DirectionalWaveguide (tin cans), ([WWW]Liege20020401)
* 3.5 km, Belgium, using 2 unmodified LinksysWET11

http://www.seattlewireless.net/index.cgi/LongShots