Municipal wifi antenna

Discussion in 'Wireless Internet' started by MTR, Oct 3, 2007.

  1. MTR

    MTR Guest

    Philadelphia's new municipal wifi network kind of sucks, but I'm trying
    to give it a shot. I'm about 450 feet down the street from a lightpole
    antenna for the network. There are leafy trees all down the street. When
    I hang my wireless router out my 2nd floor apartment window (WRT54G with
    dd-wrt) it can just pick up the signal, but weakly and intermittently.
    DD-wrt reports signal strength no better than about -72, and it changes
    constantly. So I'm trying to figure out...

    1. What kind of antenna should I use outside the window, or better yet,
    through the window? My WRT54G stock omni antennas with handmade
    reflectors barely pick up the signal. I tried using a prefab "Deluxe
    Cantenna" and it didn't help. I'm thinking that, because I'm trying to
    get signal around the trees, a directional antenna isn't the solution.
    From eBay I got really tall, supposed 9dbi replacement antennas for the
    WRT54G, and put on the reflectors, but that didn't have much effect
    either. I'm looking for a cost-effective solution - perhaps one of those
    Hawking corner antennas, to grab a focused swath of signal?

    2. An alternative is to go on the 3rd-floor roof rather than through
    the window. I'm not sure yet if I have roof access, but if I do I'm
    thinking a directional antenna might help because it'd be above the
    trees. So then there's the cabling issue. To keep the antenna cabling
    short, I guess I'd have to put my router on the roof as well (in a
    sealed plastic box?) and then run an ethernet cable down the outside
    wall and through a window. That would mean leaving a router on the roof,
    and a window slightly ajar, through an east coast winter. And providing
    power to the router! (Argh.) I don't think a USB-wifi-stick antenna will
    work - I want to run my home network (a couple desktop computers and
    Vonage) off the line, using an ethernet-fed second router. What's the
    right way to set it all up?

    Thanks for your thoughts!
    MTR, Oct 3, 2007
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  2. Just out of curiosity, which version number is your WRT54G and version
    of DD-WRT? What cantenna did you use? Where was it placed when you
    tested it? What are the settings on the DD-WRT? Is the municipal
    wireless a captive portal, does it have client isolation, what are some
    of the security factors?


    This is how I'd do it:

    1. Go into DD-WRT settings under Wirless > Advanced Settings.
    Check TX Antenna Right and RX Antenna Right
    Xmit Power 150 - 200 (initially, see how hot it gets under load)

    2. I would get a plastic weather proof box, drill two holes in it, one
    for the antenna and one for the Ethernet cable. If you don't want to
    play the power over Ethernet game you may need to get a power extension
    cord through there so the wall plug can stay inside. Use silicone around
    the holes to keep it weather proof. Alternatively you can use a solar
    panel with lead acid battery setup like me.

    3. Once in place, attach the antenna (the cantenna should be fine for
    400 meters) TNC RP plug in the, looking from the front of the device
    (side with lights), on the right side antenna jack. (If you don't get
    any signal, switch it to the other antenna)

    4. Acquire an antenna grounding adapter (they can be found online or at
    computer stores), this is in case of lightning. In your DD-WRT
    configuration Status > Wireless > Site Survey page, you will start
    seeing signals after adjusting your antenna direction. When you found
    the municipal wireless access point, click the join button.

    5. Run the long Ethernet cable that should be coming out of your weather
    proof box down to your desk or computer location. You may attach a
    switch to it so you can use more computers. Your router is acting as a
    bridge for that access point.

    6. It is wise to acquire a surge protector. One which supports RJ45
    cables. This is also in case of lightning. It will fry the cable, but at
    least your computer may still be intact.


    This is why I wouldn't do it in the first place:

    If they don't have client isolation, your security is seriously
    compromised instead of mildly compromised. VoIP is not secure
    inherently. Your clear-text passwords will be vulnerable to the rest of
    the users of that network. E-Mail and chat sessions can be read.
    Browsing habits can be watched... etc.

    Never play that "who's going to do that" card, you never know.


    If you can't do it my way, there are workarounds, but most of them are
    not pretty. Don't think you can run a simple antenna cable a long
    distance, the Ethernet cable does not endure heavy signal loss at as
    long lengths as Ethernet cables can. Mounting a large antenna out your
    window will not be sufficient in most cases if there are a lot of things
    in the way to scatter the signal. The roof provides a clearer line of
    sight. If they use an omni directional antenna at the access point
    location, try to find out where it is. Omni directional antennas work in
    such a way that being outside its Fresnel ellipsoid, can seriously
    hinder signal strength on your side. If they provide roof access, you're
    in good shape.
    dualdflipflop, Oct 3, 2007
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  3. MTR

    Ron Guest

    You could more than likely get a usable signal with a directional antenna.
    15 db to 24db increase, but low loss high frequency cable is very
    expensive.and you would need some sort of adaptor to your wireless card.
    Ron, Oct 3, 2007
  4. MTR

    George Guest

    I thought part of the deal on Philly's WiFi system is that you could
    call up Earthlink and they would install home equipment for the very
    purpose you describe at some nominal cost?
    George, Oct 3, 2007
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