Estimating path loss will indicate how feasible this may be. Some handbooks have graphs for this. The transmitter power is radiated into the solid angle of the antenna pattern and is received by the area of the next antenna. Assume that the passive link has zero dB loss. Then the next segment has an area loss also. The loss for the longer segment alone looks like more than 60dB, or around 80dB overall. I don't know what the receiver requires as signal level, but it might be -120dBm. With all these assumptions, the path would be +20dBm power with -80dB losses or -60dBm signal at the receiver site which should be plenty... in clear weather. My numbers are VERY rough approximations meant only to indicate the method of determining this feasibility. This may have adequate "fade margin" even with real numbers. > I am currently designing a Wireless Bridge between Fridley & > Brooklyn Park. The total distance of the bridge is 4.45 > miles. We cannot obtain direct line of site between the two > sites without building a 200' tall tower at the site in BP, > but both have a clear line of sight to a water tower in BP. > The distance from Fridley to the BP Water Tower is 3.88 > miles; the distance from the BP site to the Water Tower is > .941 miles. I will be using 21dbi Parabolic Dish antennas at > each site. > > The design I am proposing is to use a passive antenna array > atop the water tower, just take two 21dbi Parabolic Dish > antennas and connect them back to back using a lightning > arrestor, having one dish point to Fridley and the other to > the BP office. I figure I could pull this off because of the > short distances involved, and the customer doesn't want to > pay monthly rental fees to put a radio atop the tower (paying > for electricity & all), much less suffer the throughput loss > (from 11mbps to 5.5mbps) that one does by using a radio relay. > > I think this could work, but is there something I'm missing? > Has anyone else done this before? I'd hate to recommend > something that won't work. Chuck