This is a relatively simple practical production, the paper intends to in-depth step by step from simple to complex, if you are willing to synchronize hands-on labs, and soon you will be able to make appropriate use of FM transmitters for formal occasions. Of course, the experiment is to start from the most simple, the next diagram is a simple oscillator, which is the basis of FM transmitter.

Figure of 1.0mm enameled wire coil 3.2mm drill bit in the last 6-8 laps around, can cover 88-108MHz, 7 laps around the 100MHz. Connected by the figure, in fact, already is a simple transmitter, and power can be fired, but firing is not amplitude modulated signals, near the FM radio signal is received there will only be muted. The figure that as with modulation signals, can enter into the practical state of the.

At this point, if you will be players, VCD players, audio signals connected to the output of the transmitter audio input graph, in the vicinity can use the radio to listen to the. Although capable of firing on the map, but not practical, one is emission energy is very small, only for indoor use, outdoor open space, but also tens of meters. The second is the frequency instability, because the antenna is a wire loop through the 100P capacitors connected with the oscillation, so the antenna will affect the environment around the transmitting frequency. If you want to reach the level can be amplified in the subsequent two poles together, see below.

This is a request to be friends Dachu a power amplifier, output power is satisfactory, but there are many problems, will be described below. Oscillator and power amplifier together, it becomes a complete FM transmitter, see below.

The transmitter is easy to figure makes a successful, success is mentioned here you can plug in the antenna plugged into the working state, if the transmitter into the best hope that the state needs to do some debugging work. In fact, the fans do experiments greatest pleasure is to work through the debugging yourself more perfect, the best performance.
  First, the output of non-A state circuit, the load impedance has more stringent requirements, usually more than the transmitter output to 50O, 50O lovers experiment is not necessarily easy to find the RF cable, RF cable everywhere 75O buy Moreover, the antenna can easily make 75O, 75O output adopts therefore, the output power should be preceded by a 75O termination resistor, 75O were followed after the completion of commissioning of the antenna. 1W maximum output over the machine, do not use the kind of small 1/8W resistor, connected to the fire. Nothing burned down resistors, but the fire resistance of the amplifier is equivalent to a load, the pipe on the dangerous.
  After the commissioning of the power required for the main contents of the working point of launch tube, the working point of the harmonic components of different output is very different. Level of the local oscillator transistor operating point chosen to make it more dynamic, the measured second harmonic Bobijibo low over twenty db, four times lower, can be ignored. Close to A-level work to promote the B class state, it does not produce large energy harmonics. The key in the output stage. The choice of operating point output stage is too much trouble, the bias resistor and the 51O resistor formed under the bias should be lower than the partial pressure launch tube of the emitter voltage, so that it works in between B and C status. Close to B when used 1KO state, then launch tube operating current 260mA, output power of 700mW, the second harmonic is about 10dB lower than the main wave, three four times lower frequency energy output over 500mW.
  With the increased resistance on the bias, the working status of the launch tube close to C, the power meter's instructions'd gradually increased maximum of up to 1300mW, but this time all the harmonics are gradually strengthened, but the main wave power reduced. In the professional manufacture, not difficult to resolve this contradiction, but the circuit is designed for beginners made simple type, had to give up power efficiency indicators, the proposed use of the bias resistor 1KO. Experiment 2SC2053 serious heat, though not damaged during the experiment, estimated long-term use certainly not recommended for use when making or using two 2SC2053 2SC1970 parallel. Parallel to the attention of current measures are taken. If you just want a taste of the fun hands-on production, does not necessarily require such a large output power, how far do not need to launch, then you can make some changes in circuit parameters, circuit structure unchanged, with the 6V power supply, output power In more than 100mW, shown below.

And on the same circuit diagram, just changed the values of several components, the transistor also made adjustments. Since the output power less to do with the 3355 output tube output need not consider the security problem, you can work long-term stability.