How to Make a Stereo FM Transmitter

Anyone with the proper know-how can make a stereo FM transmitter. Just be aware that it's not as simple as making a mono FM transmitter, because a stereo signal has to be modulated together and carried on a carrier frequency. Uses for stereo FM transmitters include extending your home stereo system without wires, creating a listening aid for churches and school auditoriums and operating a student-run radio station.

Instructions

Difficulty: Moderately Challenging

Things You’ll Need:

• FM stereo transmitter kit
• Soldering iron

Make a Stereo FM Transmitter

1. Decide what you want to use your transmitter for. Some FM transmitters plug into a sound card, allowing you to listen to MP3 or other digital files. Others are designed for transmitting broadcast signals throughout your house or property.
2. Purchase a stereo FM transmitter kit online or at an electronics store. Try to find a kit whose manufacturer offers "factory assistance" in case you have any problems
3. Open the kit box. Remove the parts list and compare the list to the contents in the box. Be sure that all of the parts (capacitors, resistors, semiconductors, etc.) that should be in the box actually are.
4. Check the parts list for any items you'll need to make the transmitter, but that are not included in the kit. This could include a battery, audio cables, a CD player or an external antenna. Purchase any extra items you need.
5. Read through the assembly instructions that come with the kit before you begin assembling your transmitter.
6. Begin building your transmitter according to the instructions. You will need a good soldering iron for this step.
7. Adjust your transmitter. Keep your tests brief until you have chosen an open operating frequency in the FM broadcast band.
8. Choose an operating frequency. To comply with FCC rules, it is your responsibility to make sure that your operation will not cause interference with anyone's broadcast reception. Check the FM band for an empty frequency using a good receiving system and an external antenna.
9. Connect your FM transmitter to the main stereo system in your home. That will enable whatever is playing on you stereo to be tuned in to FM radios in other rooms.
10. Consider building a simple audio "mixing" panel or box to broadcast in a school or to an entire neighborhood. The parts are inexpensive and are available at any electronics store.

Tips & Warnings

• According to FCC rules, FM transmitters must never be tuned to a frequency above 108 MHz--specifically the band 108 to 121.94, because this band is restricted for aircraft navigation.

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