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FM Transmitter with Varactor Diode Tuning

2016-04-08 04:00  
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FM Transmitter with Varactor Diode Tuning
Presented here is a low-power FM transmitter with varactor diode tuning using surface-mount devices (SMD) that will be received with a standard FM radio. Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector. Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrast the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givin great sensitivity without an audio amplifier.