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1KM 802.11b @ 2MB

Posted by Hemos on from the if-you-build-it,-your-costs-will-fall dept.

OffTheRack writes "Check out this web site to see how a guy in Egypt built his own line-of-site (H:Get? It's Punny.) 1KM broadband connection. Plenty of nice pictures." Pretty cool set-up.

10 of 271 comments (clear)

  1. Interference by gpinzone · · Score: 5, Interesting

    Although I live in a small-ish town with presumably little electromagnetic interference, it is worth mentioning that this high-gain, 3 meter tall GSM network monstrosity is located about 7 meters away from my AP antenna, on the same roof. I really can't tell whether or not it is affecting my antenna.

    I think the more important question would be, "Is your unlicensed amplified antenna affecting their transmissions"

    1. Re:Interference by Anonymous Coward · · Score: 1, Interesting

      Who says that you need a license in Egypt to do as he is doing?
      You are equating your country's standards (I assume the US) to his. Egypt is a soverign nation and is free to do as it wishes (withing certain international legal constraints).

  2. He should try this by t0qer · · Score: 5, Interesting

    http://trevormarshall.com/biquad.htm

    I read direct TV dishes are a lot easier to build and go alot further.

    1. Re:He should try this by Lumpy · · Score: 4, Interesting

      direct TV dishes do not work well... they are not designed for the right gain that you are looking for and are more expensive than the correct dish...

      Get a set of primestar dishes... they re larger and the feedhorn on them can easily be modified for this use. I use primestar dishes only and they work awesome for my hub links.

      Primestar dishes are free, cince TCI abandoned it back in 1996 there are still many of them floating in yards or at hamfests with the reciever for $5.00

      Otherwise if you really want a good solution that is ready to go, ramsey electronics sells turnley 802.11b point to point 22dbi dishes... plug it in and you are working... no building anything.

      --
      Do not look at laser with remaining good eye.
  3. 1km? No biggie. by 4ginandtonics · · Score: 5, Interesting

    Linksys outputs 50mw. If you were to go to the FCC regulation maximum of 100mw (1 watt), you would do better.

    If you use Cisco's Wireless Calculator Excel spreadsheet, you will see that a 21 dbi parabolic dish (as seen here could grant you 76.1 kilometers.

    Now you have problems with this distance. Line of sight, for one.

    The common calculation calls for a cone shaped space from each antenna meeting at the middle. This is called the Fresnel Zone The calculator says that this zone, for 76km is 28.2 meters (92 feet). So, you have to have 92 feet of clearance. No trees. No buildings. Nothing.

    At this distance (44.5 miles) The earth curvature is 90 feet, somehow your signal must peak over that!

    So, you are going to need antenna heights of over 150 meters to set up a 802.11b wireless like of this long.

    Most engineers say this is simply not feasable. Other issues, such as antenna alighment, water (nasty multipath bounce), WiFi hotspot interferance, and the actual time it takes for a signal to travel that far are issues as well.

    So just remember line of sight. If you have clean line of sight to the other endpoint, and clarity through the Fresenel Zone, you might just have a chance for point-point 802.11b wireless.

    Cheers!

  4. 128 bit encryption internationally? by i22y · · Score: 4, Interesting

    I may be way off base here...but I was under the impression that 128 bit encrypted products couldn't be exported without a permit of some kind. The author mentions that a friend in California brought the products to Egypt. Wouldn't that be illegal to export such a product?

    And yes, I do find it cool what he did... just curious about the legality by US laws.

    --
    Mike
  5. no big deal by presearch · · Score: 3, Interesting

    I'm using a HyperLink omni and amp on a 20 foot mast on
    top of a two story farmhouse. The amp is fed by an Airport
    base station. My rev. A iBook gets 2mb from 2 miles away
    with it's internal antenna if it can LOS the antenna.

    I'm in rural flatland Indiana so it's pretty easy to spot the
    house and antenna from far away.

    I'm running below legal power limit but I'm feeding the
    antenna with a 75 ft. feed from the amp so I'm very
    sub optimal. Gotta get things spiffier in the spring
    but for now, it's cold out there. No way I'm going up
    on the roof for a couple months.

  6. Re:1km? No biggie. by pclminion · · Score: 3, Interesting
    Actually, the electrons move at about 5 millimeters per second.

    Don't believe me? Check out this. Look at the section called "Microscopic View of Copper Wire".

    The electric FIELD in the wire moves at nearly the speed of light. The electrons THEMSELVES are barely moving at all!

  7. Re:1km? No biggie. by mamba-mamba · · Score: 3, Interesting

    It turns out that what matters is the dielectric constant of the medium in which the electric wave travels.

    In the case of wireless, that medium is air, which has a dielectric constant very nearly the same as free space (vacuum).

    But electrical signals travelling in twisted pair wire (like category 5 cabling) travel a bit slower because the dielectric material they are travelling in is really the insulation in the wire. That's right, the signal is really travelling in the dielectric, not in the wires, per se.

    So the speed of propagation doesn't depend on the properties of the wire conductor, but on the dielectric in between the two conductors.

    You can calculate the speed if you know the relative permitivity of the dielectric. This is very closely related to the index of refraction, by the way.

    Anyway, in most practical situations (i.e., in non-magnetic materials) the velocity equals the free-space speed of light divided by the square root of the relative permitivity of the dielectric. So in typical fiberglass circuit board, called FR4, where the '4' represents the relative permitivity, the speed of light is C/sqrt(4), or about half the free-space speed. Since the free-space speed is 300 Million meters per second, half of it is 150 million meters per second. You could also say that it is 150 meters per microsecond, or 0.150 meters per nanosecond, or 150 mm/ns.

    But this is really only true for signals which are not on one of the surface layers. Surface layer signals experience a medium partially of FR4, and partially of air, so they travel a little faster.

    --
    MM

    --
    By including this sig, the copyright holders of this work or collection unreservedly place it in the public domain.
  8. he has clear line of sight! use laser instead by wirre · · Score: 2, Interesting

    cheaper + easier.. dunno where i found the link.. 10mbps at 1 km and gpl:ed design.. works perfect even with heavy rainstorms. http://ronja.jikos.cz/