Fm Transmitter

FM Transmitter Here is the schematic, PC board pattern, and parts placement for a low powered FM transmitter. The range of the transmitter when running at 9V is about 300 feet. Running it from 12V increases the range to about 400 feet. This transmitter should not be used as a room or telephone bug. PartTotal Qty. DescriptionSubstitutions C110. 001uf Disc Capacitor C215. 6pf Disc Capacitor C3,C4210uf Electrolytic Capacitor C513-18pf Adjustable Cap R11270 Ohm 1/8W Resistor270 Ohm 1/4W ResistorR2,R5,R634. 7k 1/8W Resistor4. 7K 1/4W Resistor R3110k 1/8W Resistor10K 1/4W Resistor R41100k 1/8W Resistor100K 1/4W Resistor Q1, Q222N2222A NPN Transistor2N3904, NTE123A L1, L225 Turn Air Core Coil MIC1Electret Microphone MISC19V Battery Snap, PC Board, Wire For Antenna †¢ L1 and L2 are 5 turns of 28 AWG enamel coated magnet wire wound with a inside diameter of about 4mm. The inside of a ballpoint pen works well (the plastic tube that holds the ink).Remove the form after winding then install the coil on the circuit board, being careful not to bend it. †¢ C5 is used for tuning. This transmitter operates on the normal broadcast frequencies (88-108MHz). †¢ Q1 and Q2 can also be 2N3904 or something similar. †¢ You can use 1/4 W resistors mounted vertically instead of 1/8 W resistors. †¢ You may want to bypass the battery with a . 01uf capacitor. †¢ An antenna may not be required for operation.