Looking for 'Tree' solution

• posted

I have two builds 800-1000 ft apart separated by trees, rural area, hills. Trees inbetween are tall enough that building a 'tower' really won't solve lack of line of sight.

How can I communicate between two linksys WRT54GSs in this situation?

• posted

snipped-for-privacy@gmail.com hath wroth:

Do these two buildings sway 100ft in the wind? If not, is the distance 800ft or 1000ft? Measure it.

You ask this as if there were no other alternatives. I suggest you look into:

1. Fiber optic cable.
2. Coax cable. RG-6/u will work to at least 900ft.
3. Wire. Gel filled CAT5 will work to about 1000ft at 10baseT-HDX.
4. Two wires using SDSL modems. 768KBits/sec maximum.
5. Two cable modems. Some of these (i.e. old Zenith) will talk to each other with proper configuration.
6. 900MHz. It goes long distances and through the trees. See:
If you insist on using a pair of WRT54GS bridges, then we need to guess at how much fade margin you're working with. 20dB is a good target value. See:
how to do the calculations. I've posted at least 20 such calculations so I'll just skip the guesswork and just throw in the numbers. I'll assume that the WRT54GS boxes are fairly close to the antenna and that you'll use the biggest practical commercially available antenna (24dBi gain).

TX power = +17dBm TX coax loss = 4dB (3ft LMR-240 plus a mess of connectors) TX ant gain = +24dBi Distance = 0.19 miles (1000ft) RX ant gain = +24dBi RX coax loss = 4dB (same at other end) RX sens = -84dBm (at 12Mbits/sec) Fade margin = unknown

Plugging into:

get a fade margin of 51dB which is excellent and about 30dB more than required. That means you can tolerate about 30dB of added attenuation from the trees and still have a useable link. I guess about 20dB attenuation per thick tree so this just might go through

1.5 trees.

Any particular type and size of tree?

Where are the hills? If in between, you need to verify that you have at least 0.8 times the Fresnel Zone clearance. At 2.4GHz and 1000ft, you need to have 8ft radius of clearance around the line of sight at midpoint. That means your antennas have to be at least 8ft off the ground.