FM TRANSMITTER RANGE – UPTO 3 KM
This F.M Transmitter has 3 RF stages. A variable frequency V.H.F. Oscillator, a class C.R.F. driver and a class CRF amplifier with harmonics filter. Block diagram of transmitter is shown below .
Power supply is 9 to 12 volts dc. RF output power is 150 mill watts. With telescopic antenna (75 C.M) range is up to 1 K.M . Range can be extended upto 3 KM, BY USING multi element yagi antenna having dipole, reflector, director elements.
Frequency of transmitter can be set within 88-108 MHz F.M band by adjusting the first trimmer. Adjust output trimmer for maximum range of transmission.
To power this transmitter user 12 Volts battery. Do not user mains derive supply.
Suggested Yagi antinna design using aluminium rods is shown here. Use 75 ohm Co-axial cable between transmitter and antenna. Inner wite of cable is connected to output of transitter and braid is connected to ground of P.C.B.
Do not switch on transmitter without connecting proper antenna.
R1 -10K Q1 -BC548
R2 -15K Q2 -Q3 -C2026 / C2570
R3-R4 -4K7 TRI – 1,2,3 – 22PF
R5 -68E MIC - 2 PIN Cond. Mike
R 6 -2K2 L1 - 7 TURN 22 SWG
R7 -22E L2 - 6 TURN 22 SWG
R8- -1K L3 -5 TURN 22 SWG
R9 -10E L4 - 5 TURN 22 SWG