Homemade C3355 transistor 1km FM transmitter circuit diagram

The picture below is a long-distance FM transmitter circuit made with an ordinary triode 3DA87C . This circuit is also an ordinary three-point oscillator circuit. The electronic newspaper explains that the long-distance transmitter circuit uses high current transmitter and can reach 1KM in open areas. The author purchased Come and assemble the components according to the schematic diagram. The components are according to the requirements in the article. The triode should be selected with a blue dot mark and the magnification is greater than 80 times. However, during the experiment, it was found that its frequency does not fall in the normal FM band of 88-108MHZ. However, no matter how the capacitance and inductance are adjusted, the frequency point is lower than 88 MHZ, which is about 70 MHZ. The author uses a TESUN radio with a TV audio reception function to receive it normally. Later, after checking the data, I found that this is the frequency point. The fT cutoff frequency parameter value of the transistor is not enough, so that the oscillation frequency cannot be increased. In order to increase the transmitting distance and keep the frequency within the reception range of normal FM radio, we have to look for other high-frequency triodes. Many electronic newspapers often introduce the use of D40, C1971, and C1972 as high-frequency oscillation or power amplifier circuits. Its high-power output increases the launch distance, but this type of high-frequency triode is difficult to buy on the market, and even if you can buy it, most of it is fake and cannot be used. Later, I found C3355. The cut-off frequency of this triode is several thousand MHZ, and its power is 600MW, which is enough for FM band. Then I made some improvements to the circuit, and I can easily create a long-distance FM transmitter circuit .

Component selection: Capacitors C2, C3, and C4 are all high-frequency ceramic capacitors, and Ct is a high-frequency semi-adjustable capacitor of 5/25P. It can also be replaced with a high-frequency ceramic capacitor of the same value after testing with a digital multimeter after debugging. The capacitor , L, is formed by winding 6 turns on an 8mm round tube of enameled wire with a diameter of 0.9, and then pulling it apart about 2CM, with a tap in the middle. The transmitting antenna is replaced by a TV antenna or a wire of the same length.

After actual debugging to achieve the best transmit power, the longest distance is no less than 500 meters.