by skeez » Sun Jan 19, 2003 9:36 am
For 802.11b (2.4GHz) you need a CLEAR line of sight for a stable network bridge. You stated you have several houses in direct line of sight between your two nodes, this does not sound encouraging. While it is possible to transmit through some obstacles, there are a number of things that can affect your signal. In fact there are too many variables to calculate and really would not be worth your time to do so. Just for consideration, the 2.4GHz signal will be completely blocked by a sheet of metal, and then it can actually be filtered or deflected by a material that the signal would have penetrated if struck at a 90 degree angle.
I would recommend you look into mounting your antennas on masts high enough to clear the other houses. If this is possible, the following calculations should get you at least an idea.
Distance between nodes: 0.44 mile = 2323.2 ft or 0.70811136 km
Your antenna height (H) can be calculated using the following formula:
H = Z+C+H
Value of the Fresnel zone: 6 (Z) - 60% for 802.11b's frequency
Curvature of the earth: .75 (C) - Plays a minor role at this distance
Obstruction height: 25 ft (H) - Average height of single story home
Result: 31.75 ft
The Fresnel zone takes into consideration objects and obstructions and their effect on radio waves. At 2.4GHz, for 1 mile use a value of 10, 5 miles: 30, and 10 miles: a value of 45.
To make a long story short, if you were to use a decent quality (5dBi gain) Yagi or another directional antenna at both sites, and got them 4 or 5 feet above the highest obstacle, then drive them both with a decent access point or bridge (30mW) you should be able to get decent 5.5mb (+/-) connection.