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FM transmitter for smartphone MP3 Player 2N2218 LM741

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FM transmitter for smartphone MP3 Player 2N2218 LM741
FM transmitter for smartphone MP3 Player 2N2218 LM741

Evolution FM transmitter with 2n2218 with audio amplification step using LM741 op amp with audio input for MP3, MP4, mobile, computer and other audio sources, beyond the traditional electret microphone. With great sensitivity to the input signal. Using fewer components and easy assembly makes it ideal for those who want even without much experience assembling an FM transmitter with reasonable power.

About the FM transmitter circuit

Circuit based on another project with transmitter 2n2218, posted on the blog.
Power supply be 6 to 12V Battery or  good quality power supply, is recommended during test and adjust use of 9 or 12V battery.
The coil should be obtained four winding turns of enameled wire 22 AWG air core self sustained and 1cm diameter. Also in this case we connect the antenna between the third and fourth loop because it ensures greater stability in the transmission.
The variable capacitor should be with maximum capacitance 30-50 pF.
If you prefer you can use an adjustable coil of this FM receiver and put a fixed capacitor of 4.7pF instead of CV.
The antenna can be a telescopic 80cm, a piece of stiff wire or a specific antenna for FM transmitter. Must be connected at the point marked by Ant and the coil is connected via C2.
As the circuit has an audio input type P2 to be connected in many different audio source, we adopted a trimpot to adjust the signal level of the circuit. Also adopted was a key to disable the electret microphone.

Use a heat sink in the transistor, which may be a commercial or DIY  piece of aluminum

TO 39 heatsink FM transmitter for smartphone MP3 Player 2N2218 LM741 Transmitters RF Fm transmitter Circuits Audio

Schematic of micro FM transmitter with 2n2218

transmitter fm 741 op amp power schematic 700x266 FM transmitter for smartphone MP3 Player 2N2218 LM741 Transmitters RF Fm transmitter Circuits Audio
FM transmitter 2N2218 schematic

Suggested printed circuit board for assembly of transmitter

transmissor fm 2n2218 potente lm741 1km pcb 700x375 FM transmitter for smartphone MP3 Player 2N2218 LM741 Transmitters RF Fm transmitter Circuits Audio
FM transmitter 2N2218 PCB
transmitter fm 741 op amp power 2n2219 layout 700x377 FM transmitter for smartphone MP3 Player 2N2218 LM741 Transmitters RF Fm transmitter Circuits Audio
FM transmitter 2N2218 PCB layout
FM transmitter 2N2218 PCB silk

Part List for assembly FM transmitter with 2n2218

Parts Value
Resistor’s 1/4 Watt 5%
R1 4.7k – Yellow, Purple, Red, Gold
R2 8.2K – Grey, Red, Red Gold
R3, R6 47k – Yellow, Purple, Orange, Gold
R4 220k – Red, Red, Yellow, Gold
R5 1K – Brown, Black, Red, Gold
R7 6.8K – Blue, Grey, Red, Gold
R8 47 – Yellow, Violet, Black, Gold
R9, R10 10K – Brown, Black, Orange, Gold
Capacitor
C1, C9 100nF – (104, .1, 0.1, or 100n) Ceramic capacitor
C2 10pF (10p) – Ceramic capacitor
C3, C7 10nF (103, 0.01, 10n)- Ceramic capacitor
C4 1µF/16V – Electrolytic Capacitor
C5, C11, C12 10µF/16V – Electrolytic Capacitor
C6 1nF (102, 1n)- Ceramic capacitor
C8 100µF/16V – Electrolytic Capacitor
C10 4.7p (4p7, 4.7p)- Ceramic capacitor
CV 3-30pF -Trimmer
Semiconductors
IC1 LM741P – Integrated circuit operational amplifier.
Q1 2N2218, 2N2219 or equivalent NPN Transistor
Connectors
IN Connector P2 – Audio Input
B Connector for connecting the battery 6-12 Volts
ANT Point to connect the antenna
Several
L Coil – See text.
MIC Electret microphone
P Trimpot 10k
S1 Switch for activate the microphone
PCB, Battery, Box, etc..

If you like assemblies transmitters see other related articles.
Download PDF files of this assembly – PCB, side copper, side components, pads, Silk, schema, Datasheet, 2n2218, 2n2219, LM741.
Download PDF      Mirror

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