> The use of primary radar requires a great deal of signal power, because objects further from the antenna will reflect or send back a weak signal. At longer di

> The use of primary radar requires a great deal of signal power, because objects further from the antenna will reflect or send back a weak signal. At longer distances from the antenna, radar becomes unreliable as a way to determine aircraft position with only reflected signals. http://www.wisegeek.com/what-is-a-primary-radar.htm http://www.wisegeek.com/what-is-a-primary-radar.htm