How to Boost an FM Transmitter

By Matthew Caines

Connect your FM transmitter to a personal audio device and you can listen to it while driving.
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Most people use FM transmitters to connect their personal audio devices to their vehicles; basically, the audio device broadcasts at a set FM frequency and the vehicle radio picks it up by tuning in. Your music is then playing wirelessly while you drive. The sound quality is usually quite grainy and distorted because of the poor frequency range of most devices; boost the transmission and improve the sound quality by soldering a copper wire antenna onto the internal electronics board.

Open the FM transmitter case by unscrewing and carefully removing the back panel. You can find the back panel screws inside the battery chamber, so simply undo the battery cover by clicking it open and pull away the cover. Remove the batteries (there should be two) and look at the cavity where they were for any tiny screws. Undo these screws with a screwdriver and pull off the back panel. Take extra care pulling off the panel because the interior electronics will still be connected by a couple of wires; avoid yanking or pulling the panel too hard.

Look at the green electronic board and find another screw. Remove any screws and gently turn the electronic board over. Also ensure that you don't pull the components around too hard; they will all be connected by small wires that limit movement so be gentle and keep the components together.

Notice the blue wire soldered to the underside of the electronic board; the wire should be soldered to the left side of the transmitter's display panel. Also look for a small black box south of the blue wire. These two things are the transmission wire and the inductor box that limit the transmission signal range. You simply need to connect an external copper wire antenna to the transmission box.

Turn your soldering iron on and wait for it to heat up. Take a covered copper wire and strip both ends to expose the copper while you are waiting; the wire needs to be only 3 or 4 inches long. When the iron is ready, solder one end of the copper wire to the underside of the black inductor box; specifically, solder it to the metal that connects the box to the green board.

Allow the solder to dry and cool for a few seconds and run the copper wire through any obvious exits on the device. For example, bend the copper wire through an external port. If there are no exits, poke the soldered wire out of the device and close the transmitter case over it; this may create a small gap in your transmitter case but the copper wire should be strong enough to work anyway.

Screw in any remaining screws and replace the batteries. Turn on your device and test it; the sound should be of a better quality and much less distorted.