Point to Point equipment

Discussion in 'Networking Issues' started by jsauve, May 14, 2008.

  1. jsauve

    jsauve LI Guru Member


    I'm setting up a point-to-point wifi link between my house and a neighbor. I live out in the woods, so my broadband options are limited. The story is too long to tell here, but here's the summary: down the road my neighbors have DSL, but because of the way the phone lines run, I'll probably never see a direct DSL connection at my house. I currently have a 256kbit link from a rural wireless provider that's way too expensive and slow.

    So, my plan is to connect to my neighbor's network for my Internet connection. I already have a 19dbi antenna and a WRT54GL running Tomato firmware. So, I'm trying to figure out what equipment to buy for my neighbor's house. I know I need another antenna, but there's a box attached to the antenna and I'm not sure what it is. The ethernet cable goes in from the router and another cable goes out to the antenna. What's in the box? A transmitter? A signal booster?


    Any ideas?

    Thanks in advance.

    - Joe
  2. danix71

    danix71 LI Guru Member

    1. Who's antenna is (figure) ?
    2. Explain exactly what cables goes out from that box. In comes the antenna cable, but what other cables.
  3. jsauve

    jsauve LI Guru Member

    I did explain the cables, but I'll say it again in more detail.

    The picture is of my current antenna which is used to connect to my rural Wireless Internet Service Provider (WISP). I would like to re-purpose the hardware to create a point-to-point link to my neighbor's DSL connection. By neighbor, I mean 1/2 - 1 mile away along a lake shore.

    The black cable you see in the figure goes from the antenna dipole to the box. I believe its a standard N connector.

    The other wire that connects to the box is an Ethernet cable that is connected to a POE injector, which is then connected to the WAN port of my router. It's hard to see how it goes into the box in my picture, but it does.

    I just want to know what's in the box. Obviously, there's some kind of interconnect between the antenna cable and the Ethernet cable. I'll probably just end up opening the box today to figure it out. I need to know so I can figure out what equipment to pick up for my neighbor's location.

    - Joe
  4. HennieM

    HennieM Network Guru Member

    Most likely there's a wireless modem in the box. A 256kb/s link is too slow to be a 802.11a/b/g, as the minimum there is 1Mbit/s.

    So, you probably have HomeNet -- router -- wireless modem === antenna.

    If you want to do a normal 802.11 wireless link to Mr. neighbor, you would probably have to throw out the modem, and run an antenna cable from your WRT directly to the antenna. You may have to change the feed horn - the little bend plate at the end of the antenna - as it may not be suitable for 2.4GHz/50ohm. If it's not a 2.4GHz feed horn, your 19dBi may become something else. It is likely though that the wireless modem is around 2.4GHz.

    Move the WRT as close to the antenna as possible to keep the cable as short as possible. Use the right antenna cable (I forget the number, but google is your friend).

    Do the same on the neighbor's side. Once you have the hardware up, 2 WRTs with Tomato loaded in place, we'll sort out the software bits, and the final alignment to get the best signal strength across the mile.

    Alternatively, replace the wireless modem with a WRT (if the box could keep a modem dry it should also keep a WRT dry ;), and do the same on neighbor's side. This has the advantage that you run UTP to the outside WRT, so no wireless signal degredation via longish antenna cables.

    If you buy WRTs, I'm sure you know to get WRT54GLs, not v5+ ones. Further, if you can't see the neighbor, you may have difficulty with signal strength. However, given a 1 mile link, with 2 x 19dBi antennas, I think you'll be OK even if you have a slightly obscured view to the neighbor.
  5. jsauve

    jsauve LI Guru Member


    Thanks for all the great advice! Very helpful!

    The antenna is currently being used for 802.11b, so the metal plate can probably stay. But, I'll keep that in mind of I start to have problems.

    The distance is actually little under a mile I think. When I wrote my first post, I hadn't actually asked any neighbors yet. Now, I've found someone that wants to do it. w00t! Their property is clearly visible from where my antenna is currently positioned on the house.

    Your assumption is correct: I'm hip to the different WRT models. As a side note on another project, I successfully setup a router-to-router OpenVPN with 2 WRT54GLs, complete with 256-bit AES encryption, ebtables-based DHCP blocking, and additional client PCs. AMAZING what these things can do.

    Thanks for the advice, I'll be opening up the box soon and ordering hardware for the other site. I will post results and progress.

    - Joe
  6. jsauve

    jsauve LI Guru Member

    Any drawbacks to using a 19dbi panel antenna instead of a 19dbi grid antenna? The RooTennas look cool because then I can stick the router inside the "pouch". Everything would be in one neat little package.

    The distance between the two points is 1825ft (~ 0.35 miles). Will the WRT54GLs provide enough umph at 42mw for that distance, or should I run 'em at 75-100mw?

    Also made mock-up poor man's POE cable today. Works great! Of course, the RJ45 connectors will be used in the final setup.

    - Joe

  7. HennieM

    HennieM Network Guru Member

    Different antennas have different specs. Whether it's a grid, panel, patch, or whatever does not really matter much.

    What you should look at (among other) are:
    1) Beam width: Grid/dish antennas usually have the smallest beam width, meaning your signal is focused in a very thin beam.
    2) SWR: This is usually denoted as VSWR. The closer to 1 this is over the 2.4-2.5GHz spectrum, or at the frequency you intend to use it, the "cleaner" (less noise) your signal would be.
  8. jsauve

    jsauve LI Guru Member

    Once again, thank you very much for the advice.

    I checked out the beam pattern chart for both the grid and panel antennas; they have virtually identical beam characteristics. The RooTenna will be best because I can mount the router (or just its guts) inside the RooTenna's compartment, thereby saving money on an extra enclosure. All of the components of this station will be in one compact package with only one CAT5 cable going into the unit. Very cool!

    - Joe
  9. danix71

    danix71 LI Guru Member

    Better advices that I could have given to you. :)
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