850 foot wireless bridge design

Sorry, my sketch didn't come thru too well. Ken

I have set up quite a few low cost systems like this for farmers. Assuming no other problems such as interference, parking machinery in the line of site etc, since it is a do it yourself job, I would start small and work my way up. You could use a couple of WAP54G's one as access point and the other one at the far end as a repeater and see what happens.

From past experience, at that distance you will probably need to use one of the 12dbi antennas at the main farm house mounted externally, and the repeater in the window at the other end.

If the connection isn't reliable then add the other 12dbi at the remote end. Sometimes you can get enough signal off of the external antenna to be functional inside the building. If you can't get enough signal inside, then you might want to set them up as a point to point bridge and add a third access point or router inside.

Some people have reported issues with the WAP54G but so far I haven't had any and have found them to be quite reliable - touch wood.

As an alternative to the WAP54G you could use WRT54GL routers running DD-WRT.

A couple of things to remember - as far as I know the WAP54G can only serve as a repeater using WEP. In point to point mode you can use WPA. The people in the other house will be on your network.

If you need to keep them off your network I would place a WRT54GL router running DD-WRT in front of your existing router and use WDS to connect it to another WRT54GL running DD-WRT sitting in the remote window. In this setup you can use WPA.

I haven't tried the 7dbi antennas before.

Selecting different channels (use 1, 6 or 11) and you shouldn't have a problem with your existing setup.

Ian

Ian hath wroth:

I've had erratic hang problems with WAP54G v3.1 firmware v3.04 in bridge mode. It does not hang in access point and access point client mode.

Yep. Recommended. However, I prefer Buffalo WHR-HP-G54.

Not so. The WAP54G in repeater mode will work with WPA-PSK. See release notes for v2.08 at:

However, in bridge mode, only WEP is supported. Strangely, it will let you configure WPA-PSK, but it will not connect.

snipped-for-privacy@verizon.net hath wroth:

Yes. Put the DI-624 wireless in the window, not the modem. The wireless needs the line of sight to the cabin, not the modem.

Not easily. It might be possible to install a power splitter at the DI-624 sending half the power to a directional antenna pointed at the cabin and the other half throughout the house.

See calculations below.

What WAP54G? In the cabin?

A WDS repeater will probably be the cheapest.

So, everything is moving to the cabin? Could you describe where the computers are located and how they are intended to connect when you're done with the system, not in its current arrangement?

Ok, lets grind the numbers. I've only done this about 20 times in this newsgroup, but once more won't hurt (much):

See examples in the Wireless FAQ at:

From what we know so far, we have 850ft range, unknown antennas, conventional radios, and are looking for at least a 20dB fade margin. I'll assume 12Mbits/sec connection speed for 6 Mbits/sec thruput. TX power = +15 dBm TX coax loss = 2dB (to window mounted antenna) TX antenna gain = unknown Distance = 0.16 miles (850ft) Rx antenna gain = unknown RX coax loss = 2dB (to windows mounted antenna) RX sens = -84 dBm (at 12 Mbits/sec) Fade margin = 20 dB

Plugging into:

and trying various values of antenna gain until I get 20dB fade margin, I get antenna gains of 7dBi each for both antennas. If you have line of sight, and a clear Fresnel zone, a pair of rubber ducky gain antennas should work. The total gain of 14dBi can be distributed unequally. For example, the stock 2dBi omni can be used on one end, with a 12dBi directional panel on the other end.

Expect reflection problems if you're shooting through a window frame.

For 850ft the Fresnel Zone radius clearance at midpoint:

must be 7.4ft. That means your antennas must be 7.4ft off the ground for this to work reliably. This may be a problem with your topography.

Change the numbers to match your speed requirements or antenna configuration that affect coax loss and antenna gain.

For a radio at the cabin end, you can use just about any of the wireless client bridge radios listed at:

that support a client mode. Not all do so please check first. I would be tempted to use a "universal" solution, such as Buffalo WHR-HP-G54, which can be configured as a client bridge or WDS bridge.

The problem with using just a wireless client bridge is that you cannot connect to it via wireless from your notebook. In order to do that, you'll need to build a WDS (wireless distribution system) bridge. WDS allows the device to simultaneously act as a repeater and an access point. Replace the DI-624 in the house with a router that supports WDS and add an identical router in the cabin. You can connect to the one on the cabin with either wired or wireless.

The catch is that you will see a 50% minimum slowdown for the wireless laptop connection, but the wired connection will run at full speed. Also, WDS setup is often a bit challenging:

(2 pages)

Depends.. How do you have power to the cabin? At my place in North Idaho, I had the sat/wireless/wired in the house, and wanted wireless back at the outbuilding (about 1000 ft from the main house), however, we had power from the house to the outbuilding, and found powerline networking to be much more reliable (winter precipitation, summer growth from the bushes/trees)..

Netgear makes two types of devices, one is a powerline bridge for wired stuff, and the other is a bridge to a remote AP (plug on in inside, the other in the outbuilding).. See the info at

usually around $99-$130 for both parts... (that's for the 54Mbps devices, same speed as wireless).. While they do make 200 Mbps devices, those are for Gigabit ethernet, Not the usual 100 Mbps stuff in most homes

If you have a wap/router in the house, just use a cat5(or cat 6) cable to go from the router part, to the input of one of the powerline devices, second part plugs in and either has a wired connection/or a wireless ap (comes as ssid NETGEAR)

Wish I had power run to the cabin. That would be a nice approach. At present, we only have generator power. I've thought I could probably power the network equipment at the cabin with 12 volt batteries if we don't want to run the generator. Seems like most of the equipment I've looked at is

Ian, Thanks for your help. I am going to take a look at recommendations from you and Jeff. I'll probably have more questions then. Ken

Jeff, It will take me a little time to digest all this and look at the equipment mentioned.. Here is more info on the existing system at the house which will continue as is after addition of the cabin internet service:

House: Satellite modem --- DI624 wireless router --- ethernet computers & ethernet printer + wireless notebook.

The cabin only needs wireless internet capabilities for one or two notebooks. The cabin doesn't need to share the house network for file sharing, etc.

I think I can get the 7.4 ft. antenna clearance above the ground at both windows. Between buildings the ground drops away considerably more. Transmission angle thru the windows will be approx 45=B0+/-.

As I mentioned, The DI624 can be replaced in the interest of a better/cleaner system if necessary. Thanks, Ken

Lots of stuff for 12v (check the trucking and RV'ng newsgroups), however, what sort of bushes/trees/etc are in the line of sight at your intended place... We ended up doing the ditch/power/powerline networking, cuz in the spring all sorts of stuff grew, and green leafy stuff atentuates a WiFi signal BIG time.... Line of sight was fine in the winter, but during the spring and summer, forgetaboutit... too much green stuff grew in the way..

Just an aside, our cabin/guest house, was about 1000 ft back on our acreage (in the forest area).. We just bit the bullet and ran a direct burial AC cable to the outbuilding (was about $600 for the cable, and $180 to rent the "ditch witch" to dig the ditch)... A bit more than we intended to spend, but figured we may as well kill two birds with one stone... (actually 3.. we also buried a 20 conductor utility cable in the ditch while we were at it, use it for phone/intercom/etc, was another $180 bucks.. Direct burial electric cables only have to be about 2ft down (perfect for a ditch witch, it only makes a 2 ft deep trench), it's water and sewer that has to be buried about 4ft down ((or at least below the frost line for your area, and sewer has to be angled/graded))).