Information on How to Make a Wireless FM Transmitter With One Chip

In order to transmit frequency modulation (FM) radio, you need a radio-frequency oscillator whose frequency changes with a control voltage. The oscillator produces the radio-frequency carrier that an audio signal can modulate. To send a radio signal to different rooms of your house, you need only a MAX2609 integrated circuit (IC) and a few outboard parts. The MAX2609 is a self-contained oscillator that has most of the workings of an FM transmitter built into the chip.

Instructions:
1.Prepare the MAX2609 by soldering it to the breakout board. Solder pins 1 and 4 to hold it to the board, then solder the remaining pins. Connect the breakout board into the solderless breadboard so that each pin sits in an unshared column.

2.Cut three 2-inch lengths of 22-gauge wire and remove ¼-inch of insulation from the ends of each. Solder three of the wires to the three lugs of the variable resistor.

3.Connect a 1K-ohm resistor between the IC's pins 6 and 5. Connect the second 1K-ohm resistor between pins 5 and 4. Place the .01-microfarad capacitor between pins 5 and 4. Insert the negative side of the 1-microfarad capacitor to pin 4 and the positive to pin 5.

4.Insert the 390-nanofarad inductor between pins 1 and 2. Connect the 2200-picofarad capacitor between pins 3 and 2. Insert one lead of the 270-ohm resistor at pin 3 and the other into an unused column. Connect the wire soldered to the wiper, or center, lug of the variable resistor to this column. Insert one of the other wires to pin 2.

5.Insert the variable resistor's remaining wire into an unused column. Connect the positive lead of the 10-microfarad capacitor to this column. Connect the negative lead to pin 2. Insert one lead of the 4.7K-ohm resistor so it connects to the 10-microfarad capacitor's positive lead. Connect the resistor's other lead to pin 5.

6.Connect one lead of the 1000-picofarad capacitor to the IC's pin 6. Place its other lead into a free column. Insert the wire at the end of the FM antenna into this column.

7.Insert one lead of the .47-microfarad capacitor so it shares the column with the variable resistor's wiper and 270-ohm resistor. Insert the capacitor's other lead into an unused column. Place the center or "hot" wire from the RCA cable so it connects to this column. Connect the RCA cable's ground wire to the IC's pin 2.

8.Connect the red wire coming from the AA battery holder to pin 5. Place its black wire at pin 2. Put two AA batteries in the battery holder.

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