This is a easy to build miniature FM transmitter that uses a minimum of
parts. although this design uses a 3 volt power source , a 9 Volts battery can be used , instead , by increasing
the value of R1 to 15K and R2 to 1K . C4 is an optional RF bypass capacitor that may help improve performance and
increase range . L1 was made by stripping 22 ga. hookup wire of it's insulation , then wrapping it in the grooves
of the screw threads of a 1/4 diameter bolt , and then back-screwing the bolt out of the resulting coil. 8 turns
were made around the bolt . by wrapping the turns in the threads , a uniform seperation was made between the coil
windings.
Reference : " Cyber Circuits "