FM Transmitter J310 Module "Little Beacon" DIY Kit

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Quick Overview

FM Transmitter J310 Module 97MHz - 102MHz DIY Kit

DIY FM Transmitter module based on J310 VCO. Has PLL compatibility. Can be tuned to desired frequency with variable multiturn resistor on the PCB. The kit include one ready hand-made coil. Tuning process is easy but require some patience.

Technical specifications:

  • Frequency: 97MHz - 102MHz with default kit coil

  • Range: up to 25 meters in open field condition

  • PLL Compatibility

  • Modulation: Wide Band FM

  • PC Line out Volume Level Compatibility

  • PCB size: 4.00 x 3.50 cm

  • Supply Voltage: 8 - 12V Regulated DC

  • Supply Current: 12.5mA at 12V

  • Easy DIY FM kit for the beginner

  • Tuning with Varaibale Resistor

  • Shipping Weight: 200 gr

  • SKU: RH-K-J310

FM Transmitter J310 Module "Little Beacon" DIY Kit Package

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  • FM Transmitter J310 Module "Little Beacon" DIY Kit
  • FM Transmitter J310 Module "Little Beacon" DIY Kit
  • FM Transmitter J310 Module "Little Beacon" DIY Kit
  • FM Transmitter J310 Module "Little Beacon" DIY Kit Package


This is education purpose DIY module project of FM Transmitter 97-102MHz. The original circuit of the Voltage Controlled Oscillator (VCO) was taken from the famous russian radiostation “Mayak” (Beacon). That’s why we called our project  “Little Beacon”. The forum thread about the VCO circuit can be found at

The circuit of the kit contain J-Fet based VCO and Buffer Stage. It do not  include RF amplifier stages because in many countries is illegal to broadcast with RF Power more than several milli-watts. The project was developed ONLY for education purpose and you have to understand it clearly. Even it has compatibility with PLL, it still stay amateur DIY device and does not fit into full technical standards of the legal FM Broadcasting.

To receive the transmitter you can use any FM 88-108 radio receiver.


Package include:

1x Carbon Film Resistor 36 Ohm

1x Carbon Film Resistor 56 Ohm

1x Carbon Film Resistor 2.2K

1x Carbon Film Resistor 100 Ohm

2x Carbon Film Resistor 470 Ohm

1x Carbon Film Resistor 15K

1x Carbon Film Resistor 1K

1x Carbon Film Resistor 1 Ohm

1x Multiturn Potentiometer 5K or 10K

1x Mylar Film Capacitor 1.5nF

2x Ceramic Disc Capacitor 1.5nF

3x Ceramic Disc Capacitro 3.3pF

1x Ceramic Disc Capacitor 15pF

1x Ceramic Disc Capacitor 22pF

2x Ceramic Disc Capacitor 100nF

2x Ceramic Disc Capacitor 10nF

1x Electrolytic Capacitor 10uF

2x RF Jfet Transistors J310

1x VHF Varactor Diode BB910

10x Male Header Pins

1x Handmade RF Coil

1x Manufactured PCB

1x PDF manual with assembling instruction


Tuning process is described in the manual. Our short demonstration video is present the basic steps of the calibration. You can tune the frequency of the transmitter with small screwdriver. The calibration steps is:

1. Tune radio receiver to 100.00MHz. You should hear the hissing sound.

2. Power on the transmitter and tune with variable resistor untill you'll hear the silence in the receiver.

3. Start play the music from the PC/CD/Ipod and adjust the volume level.


The module requires external antenna! You can use 1 meter of wire, but for better performance, quality and for reducing hum please use a dipole.


What type of signal can I broadcast?

  • Audio Mono Signal
  • Audio Stereo MPX from stereo-coder


When you are buying DIY Kit you are agree that you have certain skills and knowledge to solder it by yourself. We are not responsible if you damage the PCB or other kit's parts due to wrong assembling or handing.

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