FM Transmitter #2

This series of transmitter consists of three parts ... oscillator, buffer #1, and buffer #2. Quality of the oscillator is quite satisfactory, stable and produces a strong signal.

The first part to assemble is the oscillator. Once finished, turn on the FM radio on an empty wave. Turn on the transmitter / oscillator. Turn the ferrite core (L1) to the left / right until the radio hissing sound gone. This means that the oscillator works well. However, the transmission distance is still very limited / less than 2 meters.

Next part to assemble is the buffer 1. After finished assembling the Buffer section 1, try to test the transmitter again. The transmission distance will increase a few meters, but still not stable. Do the same thing to buffer 2.

With power output of more than 0.25-Watt, transmitter distance can be more than 100 meters, but needed a comprehensive antenna. For better quality, Q2 can be replaced with type C2053 but cost a bit more expensive. C8 and C11 can also be replaced with the size 33pf.

Using a stable power supply is a must for this transmitter to work properly. >>

Inductors Data

L1 =   0.5 mm diameter of ferrite core
P = 1 turns
S = 3 turns
Size = 0.3 mm enameled copper wire

L2 + L3 = 0.8 diameter of air core
3 turns
Size = 0.6 mm enameled copper wire


This FM transmitter used to enjoy music from PC or TV.  I covered it with DV cassette case... and added a volume adjuster (VR). Sorry about the picture quality.

Related Schematics


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