Electroneecs-project.blogspot.com Website Review

build very low cost fm transmitter, use your tv antenna and transmit upto 4km range!! the transmitter is built on a printed circuit board. this board uses track inductor for l1, l2 and part of l3. the section built around q1 is the oscillator section. oscillation frequency is determined by l1, c4 & c5 which forms the tank. actually c5 is the feedback capacitor. this is required to sustain oscillation. this also influence the operation of tank formed by l1 & c4. modulation is directly applied to the base of q1 via c2. a microphone is connected here to serve this purpose. you can alternately feed direct audio here after disconnecting the microphone biasing resistor r1. q2, q3 & q4 gradually raises the output power up to the desired level. as most of the inductors are pcb etched, there is practically very little frequency drift provided you use a highly regulated and ripple rf output from the transmitter is taken from the junction of c11 & c12. this is unbalanced output of around 75 ohms impedance. but a folded dipole is a balanced type antenna of around 300 ohms impedance. so we need to use a 'balanced to unbalanced transformer' or 'balun'. a 1:4 type balun is employed here for this purpose. antenna connection is taken from this balun via a 300 ohms flat parallel feeder cable commonly used in television to receive terrestrial broadcast. no coaxia is used to feed antenna. this saves cost. also a parallel feeder cable provides much less signal loss compared to a coaxial.  click 'read more to see details with pictures the balun is made using a two-hole binocular ferrite bead as shown above. you need to use parallel insulated twin wire to construct this. this wire is commonly used to wind tv balun transformer. if you want to get rid of this, then buy a ready-made tv balun that is generally used at the back of your television set for interfacing with feeder wire. if you prefer to build this yourself, the circuit diagram is given above. you need to carefully construct it keeping in mind about the