An FM microphone transmitter circuit is a gadget that transforms sound captured by a microphone into a radio signal that an FM radio within a specific range may receive.
Using a single NPN BC547 transistor, a simple FM microphone transmitter circuit was created.
A significant distance may be covered by the FM signal transmitted by this little FM transmitter circuit.
Circuit Working:
Parts List:
| Category | Description | Quantity | Wattage |
|---|---|---|---|
| Resistors | 330Ω | 1 | 1/4W |
| 4.7k | 1 | 1/4W | |
| Capacitors | Ceramic 0.001μF | 1 | |
| Ceramic 22pF | 1 | ||
| Trimmer capacitor | 1 | ||
| Semiconductors | BC547 | 1 | |
| Inductor coil 0.1uH | 1 | ||
| Antenna | 1 | ||
| Electret mic | 1 | ||
| Power Source | Battery 9V | 1 |
This FM transmitter circuit is intended to receive voice input via a condenser microphone.
To broadcast direct audio remove the condenser microphone and apply audio to the base terminal R1 junction.
We may extend the range of FM transmission by employing long wire or an aerial antenna.
The FM signals carrier frequency is determined by trim capacitors C2 and L1, which always select the free to use non commercial FM bands.
An FM radio frequency may be used to broadcast sound with a basic FM transmitter circuit as described in the text.
This circuit is described below in easy way:
This circuit is simple to construct since it only requires one transistor.
Adjustable Frequency:
You can alter the radio frequency within a range 50MHz to 160MHz that most FM radios can pick up by adjusting the settings of a capacitor C1 and coil L1.
Microphone Input:
An electrical signal is produced by the circuit after it captures sound using a microphone.
Minimal Power Consumption:
The circuit requires very little battery power because it just has one transistor and a few basic parts.
Though its range and audio quality may be less than more sophisticated designs this circuit is a nice place to start if you are new to FM transmitters.
Formulas:
The following formula may be used to determine the precise value of the resonance frequency of the tank circuit in the FM microphone transmitter circuit:
f = 1 / (2π√(L * C))
where,
- In hertz Hz, f represents the resonant frequency.
- L is the inductors inductance expressed in henrys H.
- The capacitors capacitance in farads F is denoted by C.
Important Note:
This calculation makes the assumption that the circuit is perfect and ignores elements that might alter the real resonant frequency, such as parasitic capacitances and component tolerances.
The circuit is tuned to a certain frequency within the FM broadcast spectrum (usually 88 MHz to 108 MHz) using the trimmer capacitor C2.
It is normally advised to use a comprehensive schematic and parts list that lists all of the component values and offers guidance for fine tuning the circuit when designing an FM microphone transmitter circuit.
How to Build:
To build a Simple FM Microphone Transmitter Circuit follow the below mentioned steps for connections:
- Assemble all the components as mentioned in the diagram.
- Connect the collector pin of transistor Q1 to positive supply of 9V battery through inductor coil L1.
- Connect base pin of transistor Q1 to positive end of electret mic and connect negative of electret mic to ground.
- Connect emitter pin of transistor Q1 to ground to resistor R2.
- Connect resistor R1 and capacitor C1 from positive supply to ground.
- Connect C2 capacitor from positive supply to collector pin of transistor Q1,
- Connect an antenna after the capacitor C2.
- Connect C2 capacitor from collector pin of transistor Q1 to between emitter pin of transistor Q1 to resistor R2
Notes:
- The transmission strength and frequencies that FM Microphone transmitters are permitted to use are regulated in most nations.
- Making ensuring your circuit runs within the law is crucial.
- The radio spectrum management department of your local government can provide you with information on these rules.
Conclusion:
To conclude, this FM microphone transmitter circuit serves as an excellent introduction to FM transmission principles.
Always put safety first by doing as advised and paying attention to local laws governing radio broadcast power and frequency restrictions.