Distance to the coil is important, I've read suggestions of upto 3m behind Quad to reduce false signals. The coil needs to be mounted on a sheet of rubber/nylon skid so it doesn't snag sticks and rocks etc. skid needs to be drawn up at the front so you can drive over logs.
Also need a flag/marker system that a second person places on the signal so your not stopping every couple of meters. If your in the desert a gps would be better coz' the distance you can cover is far greater.