This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc. The output waveforms can be both amplitude and frequency modulated. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
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Of course the recreational purpose also exists and the children will adore to have a transmitter that allows to speak for a radio FM placed at distant place and like this pretend the secret agent. The resistor R2 together with R3 it determines this amplification. Wanting a smaller earnings, because the sound tends to be distorted by the excessive earnings, we can reduce to value of R2 and R3.
After having amplified, the sign is removed of the collector of this transistor and mischievous to the base of Q2, where it modulates in frequency the sign generated by this stage.
This stage is exactly an oscillator of high frequency that operates in the strip of FM. Your frequency is determined by L1 and for the adjustment of CV. The obtained signs, already modulated in frequency, they are mischievous to a linked antenna in the collector of the transistor Q2.
The reach of the transmitter will depend a lot on this antenna, of the feeding of the circuit and of the place where will happen your operation. In open field, with a feeding of 6 V 4 piles AA and an antenna of about 40 cm of length, we can arrive to the meters.
With a smaller antenna, or in place with many structures of iron flagstones the reach will be sensibly reduced. A common wall without metallic structure is not obstacle for this transmitter. Printed circuit board bf fm transmitter circuit PCB bf fm transmitter circuit PCB List material for assembly of the micro fm transmitters with bf Semiconductors:.
BF494 Datasheet, Equivalent, Cross Reference Search
BF494 – Transistor NPN RF