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networking limiting factor for distance.....

By BlueSky
Sep 11, 2005
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  1. Hi folks,
    I have a D-Link 800AP hooked up to 50ft of quality LMR400 and connected to an 8db grey omni antenna. The antenna is mounted directly on the roof about 1ft from the roof itself.

    Now the signal is great inside the building itself, but outside the range drops out after about 75ft which is nowhere near good enough to reach the target distance that i need. The target buildings are all about the same distance away and are side-by-side so i figured the broad spectrum of an omni would be the easiest for the laptops in those buildings.

    Can anyone please help me in finding what is wrong with my hookup? Is the D-Link the problem..... the cable...... the antenna..... the height of antenna? Would using a wireless router be any better than the AP? Would something like an 18db omni be "leaps and bounds" better for distance or am i limited by the generally low mw output of the d-link AP?

    Should i get that antenna up another 6 feet or so in the air to give it some clearance from the roof?

    My goal is to be able to run across an open field about 400 yards away.
    Any suggestions would be greatly appreciated.
    Thanks
  2. jobeard

    jobeard TS Ambassador Posts: 13,368   +302

    You need a HiGain, directional antenna. With this output power, you WILL need
    to secure the network, as anyone in range will see and want to piggy-back the
    connection. (1) turn on WEP or WAP and (2) do not broadcast the SSID
  3. BlueSky

    BlueSky Newcomer, in training Topic Starter Posts: 35

    I do have a high gain cantenna, but the "beam" is only wide enough to reach the buildings within that beam and not capable of hitting the ones off to either side.

    As far as security, let's just say i am in an area where it is not important at all, so this is not an issue.
  4. Nodsu

    Nodsu Newcomer, in training Posts: 9,431

    Get a directional antenna with a wider beam (60 degrees should be more than enough) and/or put another access point in the middle of the other buildings to provide local coverage.
  5. BlueSky

    BlueSky Newcomer, in training Topic Starter Posts: 35

    I really would like to have just the 1 omni antenna to service everything within about 500 yards...... even if that means buying a 16db antenna and using a linksys wrt54g router and hack it to boost up the mw..... but was wondering if this would for sure work since my current setup seems inadequate.
  6. BlueSky

    BlueSky Newcomer, in training Topic Starter Posts: 35

    Does the height of the antenna make a difference? For example, (assuming clear line of sight no obstacles) if one antenna was placed on a pole 10 feet higher than an exact same antenna at a lower level...... would they both reach out the same distance?
  7. jobeard

    jobeard TS Ambassador Posts: 13,368   +302

    Yes, RF propogation is effected by the height of the transmitting antenna.
    However, the energy is always inversely propotional to the distance being traversed.
    There are legal limits to the WiFi transmitter power at the source,
    so
    would be a solution, IF you can cover the whole 500yrds in at least two segments.
    You could use channel 5 for the first segment and channel 10 for the second
  8. BlueSky

    BlueSky Newcomer, in training Topic Starter Posts: 35

    I have just ordered a 15db omni antenna which which is nearly 4ft high itself, and should provide much better coverage than the small 8db we have now. If that doesn't work i have a linksys wrt54g wireless router that i can apply a firmware hack to and get a nice boost in power over stock mW...... probably not legally allowed as you say..... but i plan to get this thing beat one way or another.
  9. jobeard

    jobeard TS Ambassador Posts: 13,368   +302

    go get'm :cool:
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