FM Transmitter Design




Introduction: FM Transmitter Design

About: WELLPCB PTY LTD is a daughter company of Uniwell Circuits Co., Ltd, which have two modern PCB factories, founded in Shenzhen, China in April, 2007. WELLPCB is focusing on online prototy…

Take a look on the PCB and Schematic given below

Step 1: Take a Look on the PCB and Schematic Given Below:

The electret mike encompasses a current of 200uA that changes by +- 3uA betting on sound waves. This sets the voltage across R1 to 2V and therefore the voltage across the mic to four volts. Because the sound hits the mic this through R1 will increase slightly reducing the voltage across the mic. Is that what's happening?

This dynamical voltage is passed on by the coupling cap, C1 to the bottom of the electronic transistor, that is biased by R2 & R3 to approx 2V. The voltage across R4 with no signal on the mic are Vb - zero.7 (drop across vbe), 1.3 volts. Because the voltage at b modifications R4 can change by identical quantity. This transformation in voltage is seen at the bottom of the electric circuit. And therefore the signals voltage is increased/decreased. If you closely cross-check the PCB and therefore the schematic, you'll notice that the pins on the PCB are tagged clearly to create the assembly method easier. All the element values are written properly.

Component List Required for the Project
· Microphone

· Transistor-S9018

· R1- 2.2k · R2- 22k

· R3- 2.2k · R4 - 33ohms

· R5 – 33ohms · C1- 0.1uF

· C2 – 0.1uF

· C3 – 680pF

· C4 – 30pF

· C5 – 10pF

· C6 – 30pF

· C7- 30pF

· C8 – 0.1pF

· L1 – 0.1uH

· 3V – 9V Battery

· Antenna

Step 2:

Step 1: First Use Ceramic Capacitors. Fix all of them on the board. Follow label of the components on PCB design provided by

Step 2: Also fix all the resistors after fixing the capacitors as shown in below figure.

Step 4: Fix the 5.5 turns inductor coil as shown below

Step 5: Electret Microscope

Please notice on the PCB ordered from that there's a mark with 3 lines (for negative pin) on mike silkscreen. The mark has been created for creating fastening method easier. If you cross-check real electret mike, you'll see similar solder mark. So, you simply got to match that and solder the mike.

Step 3:

The mark (solder) connected to the electret microphone is the negative pin.

Step 6: Fix antenna (ANT) and power provide connecter. Use a wire for antenna, around 10cm-50cm long. The longer the antenna the farther the transmission. You will use 3V to 9V battery for the operational the kit.

So, if you are really looking for some serious PCB design kits and particularly related to the above project, just visit

By: Shayankhan

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    5 years ago


    Can I get the PCB design ??