#3 transistor fm transmitter generator#
When the values of the capacitance of the varicap change depending on the audio signal, a frequency modulation of the generator occurs, and radio transmission begins through the induction coil L1 and the antenna.Īs an antenna, I used a piece of wire twenty-five centimeters long. Audio vibrations from the microphone through the coupling capacitor C1 fall on the varicap VD1, which is located in the loop circuit of the generator, made on field effect transistor.
And the transmission distance reaches 30-50 meters. This radio circuit is powered by a single 1.5 volt battery, because with radio emission at a frequency of 88 MHz in just 0.5 mW, the consumption is 2 mA. The radio transmission frequency of the bug can be changed by moving apart the turns of the coil.
you can use a conventional radio receiverĬoil L1 contains 6 turns of PEV-2 0.5 mm and on a frame with a diameter of 4 mm with a winding pitch of 1 mm. Radio transmission frequency 64-74 MHz, i.e. The current consumption of this design was 3.4 mA. The circuit is easy to assemble in a fairly compact design, powered by a radio transmitter from small batteries. The range of the device is about 50 meters (with a transmitter antenna length of 30.50 cm). The sensitivity of the specialized MKE-3 microphone is sufficient for detailed recognition of a whisper at a distance of 4-5 meters from the microphone. This one is enough a simple circuit a radio bug with low power consumption can be used to listen to conversations in an apartment or office, but for a short distance of 50-70 meters. Standard choke L2 with an inductance of 20 μH (it can be wound on an MLT-0.25 resistor with a resistance of at least 100 kOhm - 50 turns of PEL-0.2). L1 without a frame has 7 turns of PEV-0.35, wound on a mandrel with a diameter of 3 mm. 30 cm long with a diameter of 0.5 mm was used as an antenna.
Reception is carried out on an FM receiver in the FM range 88. The circuit is powered by a single element with a voltage of 1.5 V the transmission of sound messages from the M1 microphone at a distance of 30-50 m. Three-transistor radio transmitter circuit Fine tuning with such a coil can be performed by compressing or pushing the coils. You can make it yourself by winding 8 - 12 turns of 0.5 mm copper wire on a mandrel with a diameter of 5 mm. Resistance R1 allows you to select a channel from 88 MHz to 108 MHz.Īlmost any inductance can be used as a frequency-setting coil. The nominal oscillation frequency is set by the inductance L1 to 390 nH, which lies in the range of about 100 MHz. The built-in generator is controlled by sound vibrations. The device is assembled on the basis of the MAX2606 chip. As a last resort, use domestic microwaves, with a good margin in frequency and power.Ī simple spy FM transmitter operates in the range of 88-108 megahertz and allows you to transmit an audio signal to any radio receiver within a radius of 100 meters. Specified in the FM transmitter diagram 2N3553 RF transistors can be replaced by 2N4427 or 2N3866. Select for the best sound modulation quality. Varicaps BB204 can be replaced by conventional domestic ones. The transmitter frequency can be adjusted within 88-108 MHz using capacitor c5. Use an antenna of at least a meter to achieve maximum range. There are no coils as such, their role is played by the strip conductors of the printed circuit board. Here, the transistors are connected according to the multivibrator circuit, which operates on high frequencies- about 100 megahertz. The scheme was found in the bourgeoisie and seemed interesting and original enough to be presented to your court)) DIY audio transmitter (music transmitter)This is a fairly powerful 2W FM transmitter that will provide up to 10 km of range, of course, with a well-tuned full-fledged antenna and in good weather conditions, without interference.
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