Technical specifications Power supply: 12-14 V stab., 100 mA RF power: 400 mW Impedance: 50-75 ohm Frequency range: 87,5-108 MHz Modulation: wideband FM Schematic diagram Parts list Capacitors: C1, C2, C12 - 100 pF (ceramic) C3, C5 - 0,22 uF (electrolytic) C4 - 1,8 nF (plastic) C13, C16, C17, C19 - 1 nF (ceramic) C8, C9 - 10 pF (ceramic) C10 - 47 pF (ceramic) C11 - 8,2 pF (ceramic) C14 - 60 pF trimmer C15 - 35 pF trimmer C18, C7 - 100 nF (ceramic) C20 - 470 uF (electrolytic, 16 V) Coils: (All coils are free-standing air-core types, wound of 0,7 mm Cu wire, 6 mm internal diameter.) L1 - 4,5 coils L2 - 9,5 coils L3 - 4,5 coils Resistors: R1, R2 - 10 k pot. R3 - 33 k R4, R7, R12 - 10 k R5, R11 - 470 R6 - 27 k R8 - 22 k R9 - 270 R10 - 100 Misc.: D1 - BB409 (BB109G, BBY31) varicap T1 - BC547C (BC548C, BC547B) T2 - BFR91A (BFR96) T3 - BFR96 Antenna Power supply 3,5 mm jack CD player, computer 6 V / 0,1 A bulb Assembly and PCB layout The PCB is designed for assembling all the parts on the Cu circuit side, without drilling holes. Tuning Connect the 6 V / 0,1 A bulb to the output and use R1 to tune the right frequency. Maybe you might stretch coils of the L1. Then use C14 and C15 to adjust the highest power (the highest light of the bulb). Then you can connect antenna and audio signal. Adjust R2 until the audio sounds as loud as the other stations. With good antenna (dipole placed outdoor and high) the transmitter has very good coverage range about 500 meters, the maximal coverage range is up to 4 km.