Long-range high-frequency transistor FM transmitter circuit diagram

Posted on Nov 10, 2015

As shown in FIG ordinary triode 3DA87C to make long-range FM transmitter circuit,

Long-range high-frequency transistor FM transmitter circuit diagram
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which is normal three-point oscillator circuit, the remote transmitter circuit with large current emissions, in open areas up to 1KM, according to the schematic assembly tests, the transistor magnification to choose flag with a blue dot is greater than 80 times, but found it not fall within 88-108MHZ normal frequency of the FM band, but no matter how to adjust the capacitance and inductance in the experiment, were lower than the 88MHZ about 25 percent more than a dozen MHZ frequency point, radio with TV audio reception function TESUN radio to function properly received, fT cutoff frequency parameter value of the transistor is not enough, not to mention its oscillation frequency to go up. In order to increase the distance between transmitter and receiver can change its frequency falls within the range of normal FM radio, had to look for another high-frequency transistor with D40, C1971, C1972, or as a high frequency oscillation power amplifier circuit, with its high-power output to increase the transmission distance, but such high-frequency transistor market is difficult to buy, and even buy, most of these fakes can not be used. Later found with the C3355, this transistor cutoff frequency of several thousand MHZ, its power of 600MW, is sufficient for the FM band, then the circuit will make some improvements, can easily produce a long-range FM transmitter circuit. Select components: capacitors C2, C3, C4 are high frequency ceramic capacitors, Ct is 5 / 25P high-frequency semi-adjustable capacitor to be replaced with high-frequency ceramic value after completion of debugging test with a digital multimeter capacitance, L is a diameter of about 6 turns bodiless 8mm 0.9 enameled wire on the pipe, then opened about 2CM, center tap, using a TV antenna or a transmitting antenna in place with the same length of wire. Actual debugging to the best of its transmission power maximum distance of not less than 500 meters.

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