Monday, October 22, 2012

FM Transmitter DIY Kit with J310 VCO

FM Transmitter DIY Kit with J310 VCO

Wants to build your own FM radio station and broadcast music over your house? It will be easy with our educational diy kit of voltage controlled oscillator (VCO). The transmitter can be tuned to desired frequency with multi-turn variable resistor or with external PLL. 

The circuit of the kit contain J-Fet 310 based VCO and Buffer Stage. It do not  include RF amplifier stages because 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.

Technical Specifications:

  • Frequency: 97-102 MHz 
  • Range: Up to 25 meters
  • Modulation: Wide Band FM
  • PCB: 40x35mm
  • PLL compatible
  • PC Line Out Level compatible
  • Supply Voltage: 8-12V DC
  • Supply Current: 12.5mA at 12V
The transmitter require a regular FM 88-108MHz receiver. You can broadcast a mono audio signal or MPX stereo.
Kit package include PDF user manual with assembling process photos and calibration instruction.

PCB size is 4.00 x 3.50 cm, double layer with green soldermask and ground plane.
The PCB has reserved place for 78LXX voltage regulator, but the IC is not included in the purchase. You can use it in case your power supply is noisy. R10 potentiometer should be installed for manual frequency tuning, but if you're going to use PLL please do not solder it.
For stable transmitting range and reducing hum we advise you to use dipole antenna. Dipole design and transmitter enclosure draft can be found in our PDF manual.
Tuning process is easy but require patience because VHF device is very sensitive. If you use R10 manual tuning then even your hand over the PCB can influence the frequency. Please see two our demonstration videos with tuning.

For more information please visit our webstore for DIY Electronics -

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