125-Mile WiFi Connection

Jason Striegel writes "Team iFibre Redwire smashed the WiFi distance record, successfully linking a distance of over 125 miles at this year's DefCon WiFi Shootout. They maintained a full 11Mbit unamplified connection for 3 hours using Z-com 300mw PCMCIA cards, surplus satellite dishes, Linux, and a great deal of hacker ingenuity. The best part: yesterday afternoon they said that they expect this rig would work at distances of over 300 miles. Here's additional team info, a couple pictures of one of their rigs, and some more technical details." I still wish I could find truly out-of-the-box Linux-friendly USB adapters, so I could get some tiny fraction of this distance, cheap.

Comments

300 Miles? Not gonna happen

[Bad_Feeling]

There is just no way they can maintain 300 miles/480km without using relay stations. Multi megawatt FM stations cannot get that range simply because the curvature of the earth causes the signal to disappear into space before reaching its destination. 125/200km is about the maximum range that is possible on frequencies much higher than HF, even with captain picard's private satellite link to france they are not going to get 480km out of it.

Re:300 Miles? Not gonna happen

[dougmc]

There is just no way they can maintain 300 miles/480km without using relay stations.

Well, obviously they did it, though the site is down so I can't actually read their article.

Multi megawatt FM stations

You're probably thinking of UHF TV stations. FM stations don't get that much power.

125/200km is about the maximum range that is possible on frequencies much higher than HF,

Under normal conditions (i.e. not much altitude), maybe. But if you can put your two antennas on top of mountains, you can get further.

This page may help you determine how far the horizon is given a certain height. (And don't forget that a nautical mile is 1.15 miles.)

If we assume that each antenna is on top of a 5,000 foot mountain, with nothing in between this gives a line of sight distance of 190 miles. If we raise the mountains to 15,000 feet, the distance becomes 320 miles (though I'm not sure that sutiable mountains even exist that are that tall, that close, and have nothing inbetween to interfere. You could use an airplane or balloon instead of a mountain, but then aiming the antenna (and even getting it up there) becomes very difficult.)

This is certainly possible, and in fact if you could find the proper location (i.e. two tall mountains with nothing in between) and even bigger antennas, you might be able to go even further.

even with captain picard's private satellite link to france they are not going to get 480km out of it.

Ok, if you're talking to a satellite this all goes out the window, because it's all line of site. In that case, it's only a matter of how good your antennas are. But yes, you can get a signal to a satellite with only a watt of power or so -- hams do it all the time. And this doesn't even require really fancy antennas if the satellite is low, like the ISS is.

Re:The real question is...

[Irongeek_ADC]

I think he is referring to Lt. Bob Lozito of the Sacramento County Sheriff's Department's Hi-Tech Crimes Task Force comment in this article:

http://www.insidebayarea.com/businessnews/ci_28868 79

""They're unsophisticated but reliable, and it's illegal to possess them," said Lozito of the Hi-Tech Crimes Task Force."

Re:Working at 300 miles?

[strider44]

Going from the top of one mountain to the top of another.

Re:500 miles also done

[Ingolfke]

Interesting, but the connection wasn't 11-Mbps. It was actually only 3kbs. This is an interesting project, I'm certainly not trying to bash the work their doing. Just want to point out that the goal of the original post was broadband wi-fi, and the article you linked to was just trying to pass data over a very long distance wirelessly.

A few snippets from the article.
Non IP data were succesfully transmitted over 350 km. Speed: 3kbs troughput.

Their goal is to create a radiomodem that is capable of 64Kbs in a multislotted system

Re:The death of land lines?

[cnettel]

Sorry. The point is that both parties are using highly directional antennas. And, well, a single access point wouldn't be able to serve much bandwidth with that many users anyway. (As the contention management protocols are not really designed for 1000+ users, you will get even less than your theoretical slice.)

125 Miles tropospheric propagation

[kalevi]

All communication for longer distances than so called line of sight communication is due to tropospheric propagation.

In summertime it is very common in areas of extreme high pressure condiftions. Today it might work just fine, tomorrowe no connection.

Best of luck with your experments!

Kalevi Nyman
SM0NTE
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Re:The real question is...

[Chanc_Gorkon]

Depends. If your a LICENSED Amateur Radio Operator, cantennas and this dish used for the record are legal. Anyone else, like 90 percent of us who use WiFI, it's not legal. Only the antenna that comes with your equipment or is designed for use with that equipment (like DESIGNED to work with it)can guarantee that you stay udner the FCC's regulated ERP rules. Will the FCC do a enforcement action? Not likely. Does podunk Police officers have the right to confiscate your equipment? NO. In the US, the FCC is the ruling body responsible for regulating RF. The local law has no jurisdiction on it. It would be called a Federal Premption.