Trying to confine a wireless signal to your home is not a practical solution to security concerns. The distance that a wireless signal will travel is mainly limited by the receiving antena and sensitivity of the receiver. An ordinary wireless receiver can probably pick up your signal for 200 to 1000 feet. A great receiver could probably pick up your signal from a mile or more. The best alternatives are:
a) convert your system to a wired system, or,
b) encrypt your wireless using a good encryption method (WPA or preferably WPA2) and use a strong password.