Work
  As shown, the transmitter is amplified by the low-frequency, varactor bias, the oscillation circuit. BG1 amplified by the audio signal, sent to the varactor, with the capacity to signal changes, the direct FM oscillator circuit, eliminating the use of the parasitic transistor junction capacitance AM FM phenomenon of harmonics less. Has FM radio signal directly from the L1 to space radiation.
Component selection
  Inductor L1 with 1mm enameled wire in the tube ? 8mm 5 on the turn around, bodiless hollow. L2 with 0.1 ~ 0.3mm enameled wire in the carbon film 1/4W resistance is greater than 100kO resistor from around 100 turns, weld in resistance at both ends, C2, C11, C4, C3, C5 should be used high-quality ceramic capacitors. Resistors are used 1/8W, 0.01µF decoupling capacitors to use ordinary ceramic capacitors.
Installation and Commissioning
  Recommendations made by etching circuit boards, the first welding RC components, semiconductor components and then welding, welding inspection is completed correctly, the pass on the +6 V power supply, measured in 9014 due to the emitter voltage of 0.47 ~ 0.9V, if not on should be adjusted R1. Test-retest 9018 emitter should be 1 ~ 2V to-ground voltage, if not on the adjustable R6, and then measured the bipolar varactor should be no voltage, or bipolar voltage difference is less than 0.25V. If the polarization of pressure is too large, adjust R3 or R4. To adjust the above items, turn on the radio FM section, the transmitter transmitting the signal received, opened to a distance of more than 5 meters, if the transmitter sends no signal, adjust L1, stretching L1, fundamental frequency increased, the compression L1, fundamental frequency decreases, the frequency of the transmitter to avoid transmitting the local radio station, but also a reliable receiver. Draw a line on the output signal-player and other equipment, carefully adjust the W1, the music in large volume without distortion is good (not open to-player and other equipment to the maximum volume, but to open the volume in the common position). After the adjustments above, the basic end of the commissioning will be loaded into the solid plastic or wooden box (not with a metal box), to be decorated, used to listen to music or for TV audio transmitter, and FM radio signals are the same, clear and stable, can be called a "professional amateur transmitter." And without the antenna, the volume and small, for use at home without fear of the firing distance.
  I use it for TV audio transmitter, audio input connected to the TV's audio output, battery with a 6V power supply, with a crocodile clip as a switch. Circuit board with rubber bands tied to the battery, and continued with dozens of days, do not have to worry about battery run out.
Experimental Reviews
  The transmitter producing simple, reliable and low cost. Specific production, the author used a small circuit board for the high-frequency loss of the epoxy board, debugging is completed, the high-frequency coils are made of high quality wax seal, very good. 5pF capacitor can be used instead of double-sided Bonded Copper (at 1pF = 1 ?? millimeters).