This wireless microphone circuit uses only a single transistor, with few additional passive components. This FM transmitter is very compact and need only a single cell 1.5Volt battery, even works on 1.2V rechargeable battery. Here is the schematic diagram of the circuit:
The transmission range could be between 30-50m radius in open air, and practically depends on the surrounding transmission path and obstacles. The transistor is not critical, any transistor with high hFE, high frequency bandwidth (more than 150MHz), and low base-emitter capacitance will work: 2N2222A, PN2222A, BC109B, C, BFxxx series, and even well known BC238 is suitable for this transmitter.
The inductance L is the critical part and should be handmade. Use an AWG24 (0.5mm) enameled copper wire and make 2-4 loose turns with about 4-5mm diameter. Try to loosen or tighten the coil, or trim the variable capacitor, and try to receive the signal on around 90MHz. Don’t forget to tighten the coil using a glue to fix the coil, avoiding mechanical deformation that change its inductance value.
Possibly Related Articles:
- Simple 9V Wireless Microphone FM Transmitter
This FM transmitter circuit can be used as a wireless microphone, can be received by an ordinary 88- to 108-MHz FM broadcast receiver. For the power supply, this transmitter circuit... - Two Transistors Wireless Microphone (FM Transmitter)
Please be warned if operating this circuit might violate the regulation of your country, because this FM transmitter circuit radiate strong radio frequency to the environment. This wireless microphone is... - Single Transistor Microphone Pre-Amplifier for Both Dynamic and Condenser Type Mics
Condenser microphone and dynamic microphone (moving coil microphone) has different characteristics. For dynamic mics, a biasing current is not needed because the transducer generate the electrical signal. In condenser mics,... - Another Small Single Chip FM Transmitter
This FM transmitter circuit is small, similar to our previous single chip FM transmitter, but this FM transmitter is monophonic. You can see in the circuit’s schematic, the left and... - Single Chip Stereo FM Transmitter Circuit: A Very Compact Design
ROHM (www.rohm.com) is originally a resistor producer company, but finally expand their business and produce monolithic IC, and this one used in our circuit is the example. The internal structure... - LM10 Single-Cell Microphone Amplifier
This is a Single-cell microphone amplifier circuit. This circuit produce a voltage gain of 60 dB at 500Ω load with bandwidth 5kHz. This circuit can provide a 60dB gain up... - Tachometer Circuit with Single Transistor
A schematic diagram of simple tachometer circuit is shown below. Using only a single transistor as the active component, this tachometer would probably be the simplest one. The input of... - Single Transistor Blocking Monostable
Below is a schematic diagram of blocking monostable circuit. The normal state of the transistor is off because the 10 k resistor has been removed. The conduction will be started... - Single Transistor Blocking Oscillator
Circuit below is circuit of a transistor blocking oscillator. The transformer is phased. This cause any increase in collector current pulls the base up, further increasing the current. The transformer... - Complement Phase Inverter with Single Transistor
This is a complement phase inverter circuit. Sometimes this circuit called a paraphase amplifier circuit. This circuit has two output signals that is have sufficient “headroom” because this circuit is... - Single Transistor Lead Acid Battery Monitor
We can make a very simple battery monitor using a dual-colour LED and a few additional components. When the red and green LEDs are illuminated, the LED produces orange. The... - Single Transistor Half-Wave Peak Detector Circuit
Using only a single transistor and few passive components, you can build a fairly sensitive peak detector. circuit This peak detector circuit is suitable for audio application, since the average...
| 
