The following FM transmitter circuit is MPX96 low-power FM stereo broadcast transmitter kit from North Country Radio. The transmitter circuit is suitable for you who want to deepen the knowledge of FM transmitter building blocks. You can sort the block or modify it.

As we know, that FM transmitter broadcasts have stereo sound. A audio stereo encoder circuit to complete part of a mono FM transmitter circuit. This device function is encoded two-channel sound signal with the pilot’s guide 19 KHz tone that is mixed with a balance modulator. The FM transmitter circuit uses a MC145151 PLL Synthesizer IC from Motorola, and uses the 74F160 as a frequency divider from the oscillator output frequency. Further frequency programmable via a DIP switch based on a binary table. For more information can follow the link below.

FM Transmitter Circuit Board

MPX96 FM Transmitter Circuit Board

Some parts of the circuits that need to be modified to include:

• Repair or installation of low-pass filter on the audio input to prevent the occurrence of chirping sound.
• Filtering frequency10 KHz crystal for it prevents the reference appears in the unit’s modulated output.
• The phase-locked loop (PLL) controlling the unit’s carrier frequency was insufficiently damped, Causing the PLL to “fight” the modulating audio at low frequencies.

The modifications outlined here range from easy on-board component changes and additions, to fairly involved external circuits added to the audio signal path.

MPX96 PLL Synthesizer Stereo FM Transmitter (North Country Radio)
MPX96 FM Stereo Transmitter Circuit (Modifications)

With experiments on a circuit to add to the experience or ability to be creative and can help in overcoming problems that arise. Through the link above is expected to provide insight for those of you who want to build an FM broadcast transmitter of an FM transmitter circuit.