How to Eliminate Static in an AM Radio in a Truck

AM radio static in trucks is relatively easy to eliminate.

AM radio signals are particularly susceptible to much more radio frequency interference (RFI) than FM stations. Since ignition and other truck systems both utilize the same 0.5 to 1.6 million hertz range, annoying humming, clicking and whirring sounds may be present when listening to AM radio in a truck. Listening to AM radio in trucks can also be more challenging since the radio waves are constantly being inundated with magnetic pulses from the truck's mechanical systems.

Things You'll Need

• Wrench
• Screwdriver
• Inline noise filter
• Resistor spark plug wires
• Ground strap

Instructions

1. Diagnose what the problem could be. Disconnect the antenna in the truck if possible. Start the truck and tune the AM radio to a clear channel. Put your foot on the gas and listen to the static. If it sounds the same as it did when you first put the channel on, the source may be the electrical system and power wire supply. Have the electrical connections inspected, including the grounding devices.

2. Ensure there is adequate contact between the vehicle and the antenna. Check if the antenna cable does not have any corrosion and is tightly fitted. Corrosion can greatly interfere with AM signal transmission. Remove any corrosion by first taking the antenna off the mounting. Use a vinegar solution or using an acid or gel chemical. It may be necessary to use a mechanical method like grinding or blasting.

3. Clean and replace corroded cables as necessary. Ensure that all are metal-to-metal contacts. Replace the truck's spark plug wires with resistor wires, as they can cause ignition noise that interferes with AM radio transmissions. New resistor wires will eradicate RFI through controlling the high energy ignition pulses. Check that the battery terminal and ground point on the chassis have good contact with the negative battery cable. Otherwise, bad connections may cause circuits to interfere with radio reception as they go along incorrect routes.

4. Install a noise filter in the AM radio's power cord by clipping the red power wire in the back of the radio and soldering the inline filter. Ground the filter beneath the dashboard of the truck to a steel component. This may work to stop noise from other circuits as well as the alternator.

5. Use a flexible copper braided ground strap between the firewall and the hood of the truck. This is so that the body of the truck and engine use a common ground, which serves to eliminate AM radio interference. Use original screws and bolts to secure the strap and scrape mounting surfaces of corrosion if necessary.

6. Check for weak AM radio reception. Take a portable radio into the truck to see how the reception is. If you can hear the radio just fine, your truck probably has an antenna problem. All vehicles, especially trucks, can be susceptible to excessive movement. Also, if your truck is an older model, this could indicate that insufficient AM reception could be coming from the antenna's base or from inside of the fender region.

References

• C. Crane: Car Radio Reception
• Just Auto Repair: No/Bad Radio Reception