How to Convert an AM Car Radio to FM

by William Jensen
vintage car. image by Victor Samoilovich from

If your old car has an AM radio, you can obtain more stations and better sound quality by converting it to FM with an FM car radio converter box. These boxes essentially work the same way as digital TV converters: the FM signal comes through the antenna and enters the box's tuner. Then the converter transfers the audio to the car radio through an AM frequency, so the radio simply treats it as a strong AM station. It effectively replaces the tuner, but continues to use the same antenna, receiver and speakers.


Step 1

Obtain an AM to FM car radio converter. As of late 2010, eBay's completed listings show these converters generally sell for around $30 to $65, including shipping costs. Try searching for "fm radio converter" on eBay, but ignore the "FM Band Expanders" and Japanese FM band expansion units.

Step 2

Attach the converter to the car's electricity, AM radio and antenna. According to, you should connect the converter to the "fuse block" for power, attach its output to the radio's antenna input and connect the car antenna cable to it. Ensure that each wire runs to the correct sockets on the radio and converter. Now you're ready to convert FM signals to AM.

Step 3

Switch on the converter and tune the AM car radio until you find the converter's frequency. Then use the converter's tuning knob to find an FM station. Switch off the converter and tune the radio normally to hear AM stations. Some converters have an AM/FM button and allow you to accomplish all tuning via the converter.

Verify that you connected the antenna cables securely, if sound or reception is poor. Fine-tune the AM radio to ensure that it's picking up the converter's signal as well as possible. Some FM converters have an AFC (Automatic Frequency Control) switch; engage it after tuning in a station, to limit distortion and prevent broadcasts from drifting.


  • Some companies like offer services to install FM capability in an existing AM car radio.


  • Put the converter in a safe place where it won't move around with changes in direction or speed.
  • Use care when conducting electrical wiring.

Items you will need

  • FM radio converter box

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