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!

Re:Homebrew

[Anonymous Coward]

The University radio club I belonged to in the 70s was given a klystron. I don't know the power, but it arrived on a truck, was lowered onto the pavement by crane, and shape and size was roughly that of a jet engine.

Re:Homebrew

[WhiteDragon]

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.

If he is many miles away, the signal will have attenuated to usable power levels. This sounds like a good way to go, but the question is, can he modulate the signal?

Re:Homebrew

[JUSTONEMORELATTE]

haven't the slightest clue what that means

Do a Google search for klystron.

Nah, I think I'd rather post to /. with a lead in line of "I haven't a fscking clue what I'm talking about."

Re:Homebrew

[theLOUDroom]

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

Well duh!

He needs to blast TWO signals!

So as long as he can dig up another 20kW transmitter, he should be set .
Yes, he will probably fry everybody else's equipment, but more importantly he will probably be able to establish a link whose distance is limited by the earth's curvature or his ability to put a laptop into space.
I think we can all agree that either would be pretty sweet.

To be immediately followed by chinese food...

[Ammishdave]

Now all the slashdotters will pull out their favorite cooking utensils

Patriot Act

[vi (editor)]

Don't you fear that the FBI will use the Patriot act to raid the conference ?

Re:Patriot Act

[Lord Kano]

Don't you fear that the FBI will use the Patriot act to raid the conference ?

I'd bet that a good 10% of the attendees in previous years were either FBI agents or informants. Since not too much unsavory activity goes on at these kinds of cons, I doubt that they're all that busy.

LK

Re:Patriot Act

[martissimo]

oh come on, you get a free "spot the feds" t-shirt in return for having your own file opened by the govt. ;)

Re:Patriot Act

[JWSmythe]

If they're just opening the file on me, I'd be surprised.

Too bad I can't make it this year. I made plans, thinking DefCon was in mid-August. Oops.

This sounds like a game I'd like to play (the wireless thing). Spotting the feds would be too easy. Now, bugging the Fed's phone would be more fun.. :) Wiring a feds room for video and sound, *THAT* would be entertaining.

Re:Patriot Act

[pclminion]

Are you serious? I'll bet you $100 the FBI runs the damn conference.

Every year, predictably, a large number of hackers (and, admittedly, a much greater number of wannabes) show up in Vegas. They get drunk and chatty, and spill their guts to each other on the latest techniques. Why would the feds rain on that parade? It's like a tap directly into the hacker underworld.

wohooo! radiation!

[tciny]

In other news: Attendees wont need to bring any cooking equipment.

Re:wohooo! radiation!

[Anonymous Coward]

all attendies will hereby be rendered strile. This dosen't matter though since they are regular slashdottters.

Re:wohooo! radiation!

[guile*fr]

you dont cook snack bars, except when you forget one
on a overheating computer.

Wrap it up

[smiley2billion]

Sweet Jesus, everyone invest in Reynolds Wrap now!

I would

[lachlan76]

I'd enter, but I can't take off my tinfoil hat to use as a reflector.

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. :)

Re:Passive Relaying?

[germ!nation]

and thus making WiFi reliant on wires. 'so crazy it might just work'

Re:Passive Relaying?

[Anonymous Coward]

can i use my 100' tesla coil?

Re:Passive Relaying?

[Anonymous Coward]

I think the funniest thing is that he thought it had something to do with humous. In fact, I would have modded his original question with the google link as +3 or +4 funny.

35 miles?!

[flopsy mopsalon]

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

Re:35 miles?!

[InternationalCow]

They are probably using a big sewerpipe :)
Always knew that one day, wi-fi would go down the drain.

56.3 km

[geirt]

35 miles = 56.32704 kilometers

Re:56.3 km

[tpgp]

56.32704 kilometers

uh huh. I'm sure they measured to the centimeter - do we really need 5 decimal places for the ks equivilant of 35 miles?

On a more serious note - I and most people who read international articles are well able to deal in miles or kilometers.

Not that slashdot couldn't be a little more international mind you.

Re:56.3 km

[Patrik_AKA_RedX]

It would be conviened if we made it a habit to write 35miles (56.3Km) and visa versa.

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

Re:Not necessarily power limited

[RogerWilco]

Thank you,

I thought I remembered that typical horizon is 25-50 km, now I do not need to dig up the numbers.

Re:Not necessarily power limited

[JWSmythe]

I thught horizon was 15 miles from a viewer at sea level on flat terrain. But ya, they'll need good altitude at one or both ends.

Re:Not necessarily power limited

[elgatozorbas]

I thught horizon was 15 miles from a viewer at sea level on flat terrain. But ya, they'll need good altitude at one or both ends.

It is impossible to say 'at what distance' the horizon is without knowing how high you are from the surface. At zero level, the horizon is at distance zero. The figure you are quoting may be the distance to the horizon for an average person standing.
In my previous post, I left out a discussion about the earth's atmosphere: in reality, the radio waves (or light waves) don't follow a straight line, but a somewhat curved path which (depending on the weather circumstances) helps you 'look around the corner', or 'sends you into the ground' (such that you need a higher tower to compensate for this). Propagation calculations take this curved path into account by using a straigth path, but changing the Earth radius for the calculations.
(And then there are some other simplifications, like not taking into account Fresnel zones, interference, etc)

Z

Re:Not necessarily power limited

[Kallahar]

Last year's 35 mile shot was indeed over the horizon. The team had to hike up a mountain in the rain to get high enough to make the shot. They actually assembled the antenna right there in the wilderness!

Re:Not necessarily power limited

[JWSmythe]

Ya, the viewer I was refering to would be an average person standing. My dad told me a long time ago that it was 15 miles. He explained it to me once when we were at a beach, looking at boats on the horizon, and we could see them disappearing. i.e., viewer at sea level. :)

He was a research scientist, so most little tidbits like that were fairly accurate. I never bothered to figure it out.

You're right about the not quite straight path. I have an excellent book on microwave communications, which does talk about paths bending over mountains, and the atmosphere bending signals. They were still pretty clear that you want to be able to see your target (at least theoretically, if the distance is far enough), without anything near your path to interfer with the fresnal zone. At 40 miles, if you only just achieved line of site, the ground would seriously interfere with the signal.

I'm lucky with my long distance 802.11b connection, it goes from a 2nd story roof top, to the 10th floor of a building. It's only 1/2 mile, but I have perfect line of sight. I had to trim a few trees close to the house side because when the wind blew, the top of it would come into my fresnal zone and mess up my signal. Once I got rid of the damned trees, it stays at 100% signal strength all the time. Wheeee! That's with a 24dBi parabolic dish, and a 14dBi panel, and Linksys WAP11's at each end. Having good antennas is a great thing. The same WAP11's with the stock omnidirectional antennas were lucky to get 85% signal strength across a room in the same building.

Hams have the 10 Watt advantage!!!

[ivi]

From my last visit to a retailer, I took away the suggestion that WiFi might be running on the order of 100 mWatts at GHz freq's.

Well, the new ICOM digital radios operate on 1.2 GHz with 10 Watts of transmit power.

Reviews suggest that mobile nodes can maintain
reliable links to other nodes while driving
around town.

Worth a look:

http://www.HamRadio.com/pdf/dstar.pdf

Oh, if you win, just earmark my 10% of your prize's $-value to me at... ;-)

Re:Hams have the 10 Watt advantage!!!

[chamcham]

If I can use my HF Packet Modem I'll warm up the AL-80B for the competition ;)

1kwatt of RF goodness.

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

Re:Other records

[remin8]

WOW 82 miles.... where did I put that 1500 mW transmitter?

Last Year's Record

[john_smith_45678]

Last year's record is mentioned in this article:

Wi-Fi Fidelity
Wireless technology opens up a world of possibilities--and a can of worms
http://www.meetingsfocus.com/displayarticle.asp?id =2483

Wifi shootout...

[dj245]

...Where the range of your unprotected wireless network is longer than the range of the gun you use to chase people away from it.

Re:Wifi shootout...

[JWSmythe]

In past years, they've had shooting (like bang-bang guns) contests. so this may be more accurate than you may think. {grin}

Or Not?

[IcEMaN252]

Hope to see you there.

You won't see me, I'll be too far away.

I think I can win this....

[dave-tx]

Finally, a perfect application for my 40-mile-long wifi antenna... made out out of cat-5 cable.

Re:I think I can win this....

[JWSmythe]

Ummmm.. Ya..

Be careful, someone may take that seriously. :)

"Hey Dave, I ran 40 miles of Cat5, and it doesn't seem to work!"

Re:I think I can win this....

[celeritas_2]

heh....excellent idea but isn't CAT5 limited to about 100 meters? I would imagine 35 miles of cable would have just a _little_ resistance.

What would really impress me wouldn't be 35 miles

[usurper_ii]

line of sight, it would be a three to five mile radius working through trees...and even hills. Now someone pulling that off cheaply and legally would be like pulling Excalibur out of its rock and it would impress the hell out of me. (by the way, I'm involved in a wireless ISP that is getting hammered by the local terrain).

Usurper_ii

What about speed of light?

[Dr. Manhattan]

Hmmm. What's the limit on the timeouts of the protocol, vs. the speed of light? Even with lots of power and directional antennas, eventually there will be a distance where connection is impossible just becuase the ack's can't get there fast enough.

Seems timeouts range up to a second or so; hundreds of milliseconds to authenticate. So you're not going to see anyone much further than 186,000 miles. :->

So if

[kc0re]

So if people can go to these competitions and shoot 35 miles, can someone come to my house and see why my lappy won't work on my back porch. K-Thanks.

Curvature of the Frigging Earth

[bugmenot]

The horizon is about 35 miles away. If you get much further than that you are in an airplane.

Re:Curvature of the Frigging Earth

[Anonymous Coward]

at 2.4 Ghz the horizon is 1.22 X the square root of the hight.

Re:Curvature of the Frigging Earth

[pclminion]

The horizon is about 35 miles away. If you get much further than that you are in an airplane.

Maybe in Nebraska, but I've personally stood on a mountain top and seen nearly 200 miles (196 miles to be exact, the distance between the summit of Strawberry Mountain and Mount Hood in Oregon). It depends where you're standing, and what you're looking at.

35 miles?

[Kvasio]

http://it.slashdot.org/article.pl?sid=03/09/23/123 3219&tid=193

As if I needed another excuse to say....

[asink]

Mine is longer than yours.

Yes, I am actually going again this year, so this is a joke.(or so you think....)

Re:As if I needed another excuse to say....

[Anonymous Coward]

repeatedly saying something does not make it true. (current US admin. notwithstanding)

Rule of thumb

[Teun]

In a flat country like The Netherlands an old rule of thumb for microwave towers is a 50Km distance between two 50m towers.
Your 200ft example is about 60m and 27Km till the horizon is a little over half that 50Km for one tower so the old rule seems to be right.

Re:What would really impress me wouldn't be 35 mil

[Phishpin]

You wouldn't happen to be in the Evansville, Indiana region, would you? They're moving to a new system even less able to shoot through my treeline and need to put up a mast that I have been thinking about mounting lasers on to protect me from the bad people.

A thirty foot mast on top of my (three story, counting attic) house just looks silly. If someone could figure out how to blast through these damn locust trees with a dish mounted at ground level, that'd be gravy.

I don't think they could go any higher, either. 250 feet is pretty "up there."

any neon signs?

[Anonymous Coward]

small question, since we already got
the USB Wifistick in a parabol dish setup ...
all the antennas are "passiv", can't one add
just like a neontube of somekind, to the middle
of a parabol antenna?
as far as i know about antennas, these are just
sticks of conductors, and the electrons go up and
down, radiating a electro-magnetic field.
now think what is happening in a neon tube.
the electrons exit one point and smash into the
other end. you can use A/C on neon tubes plus ALOT
of voltages. should work as a "plasma antenna".

maybe you can stack them neontubes parallel, tie
a whole bunch together ... run different
frequencies or something ...

Re:any neon signs?

[Anonymous Coward]

links:

http://mitglied.lycos.de/radargrundlagen/roehren /t u05-en.html
http://en.wikipedia.org/wiki/Magnetro n
http://www.raytheon.com/about/tech.htm
http:// www.marklandtech.com/news/042104_antennawif i.html
http://jlnlabs.imars.com/plasma/gmrtst/
h ttp://mitglied.lycos.de/radargrundlagen/roehren/t u05-en.html
http://www.buergerwelle.de/d/doc/gesu nd/munzert-di rected-energy-weapons.htm

Klystron wikipedia link

[j1m 5n0w]

Klystron

-jim

Yeah but can it . . .

[Anonymous Coward]

put out more energy than my Positron Collider

Re:What would really impress me wouldn't be 35 mil

[bill_mcgonigle]

If someone could figure out how to blast through these damn locust trees with a dish mounted at ground level, that'd be gravy.

Don't bother at 2.4GHz. Have you looked into a 900MHz solution? You might be able to repeat it to 2.4GHz at the other end of the locust forest if you can get power to a pole out there.