Circuit diagram 500mW FM PLL transmitter 88-108MHz using LMX3206 and PIC16F870

This oscillator is called the Colpitts oscillator and voltage controlled to achieve the FM (frequency modulation) and PLL control. T1 must be HF transistors to work well, but in this case I use a cheap and common BC817 transistor. LC tank oscillator needs to oscillate properly. (I must warn you that the signal is not symmetrical in form. Pulsa pos

itive only a few microseconds, so you will be hard to see on the oscilloscope. ) I solved by connecting it to 74HC4020 (14-stage Binary Counter) to input pin 10 Hours. In Q0 (pin 9) you will have a symmetrical square wave with a frequency half since the circuit is a table. In Q1 pin 7 will be divided by 4, see data sheet for more information. A potentiometer P1 was added to adjust the depth of modulation (FM Wide or Narrow FM). You may have to play a bit with a value of P1 because it tends to modulate the lot. You may need to add the 500k 1M potentiometer only. You test and find out for himself. Resistor R1 and resistor Re2 regulate the flow of DC. In this case I find that 9. 1k will give a good output power and thus equal to 150. If you want to increase the power should be lower Re2. You can add another 150 ohm resistor in parallel.

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