easy to build...!..watch also "EMF Detector homemade AC/DC Version and EMF Detector homemade  Part 2 ..Part 2.1 ..Part 3 ..etc.." if You want further information about this project ...!.. ..the  antenna is 4 inch (100 millimeter) long  simple circuit. finding live wire inside the wall...etc.
! ! !      If these transistors are not available in your country     (BF 246 C and BC 337) ask "google" for equal type  transistors ! ! 
It works with indication LED. usefull tool for finding live wires inside the wall or other low frequency radiation.It works for radiation nearly up to 100 000 herz.