How to Build a Noise Filter for a Radioby Owen E. Richason IV
If you have a radio you enjoy listening to but cringe every time a television or the microwave causes strange noises to emanate from it, then you can apply a simple fix. When radios are powered on, the antenna isn't the only object that receives signals -- the power cord does as well. Interference picked up from other electronic devices causes a buzzing or static in the sound coming from the radio. You don't need to actually build an elaborate filter to reduce or eliminate unwanted radio noise. Instead, you can use a simple device.
Unplug your radio from its power outlet and let the power cord cool if hot. Disconnect any other audio cords running to your radio.
Pry open the noise-filtering bead's cylinder or outer casing with your fingers. The filter is oblong and typically covered in plastic casing. You will see an iron core of beads or a solid piece of iron inside the ferrite line filter which blocks interference emanating from other electronic devices.
Place the opened ferrite line filter next to the power cord's plug and snap it shut over the radio power cord. The filter will be in an open position. Sandwich the power cord into the open filter, near the radio's power cord plug and close the filter casing shut.
Plug the audio cords and power cord back in. Turn your radio on and test the noise filter by turning on another electronic device such as a microwave. This should block interference from entering into the power cord and causing noise.
- If the noise level remains unchanged, reposition the ferrite line filter on the radio's power cord and test it again to find the best location to reduce the interference noise.
Items you will need
- Iron ferrite line filters
- "New Fix-It-Yourself Manual"; Reader's Digest; 1996
- Electrical Engineering Times: The Elegance of Ferrite Beads as a Circuit Design and Problem-Solving Component