AM Signal Issue Diagnostic Tips

A. AM Signal Issue - Diagnostic Tips

First, it is important that you compare the reception performance of the complaint vehicle with the reception performance of other vehicles with known good reception. You should use the same set of test stations in the same locations every time you test a car, in order to become accustomed to how the stations should sound and what external interference is to be expected. This should be done with the engine running and with the engine not running and note the difference.

It is important to note that even with a perfect AM radio receiver and a perfect antenna, reception conditions are constantly varying. Interference from noise sources, both internal to the vehicle and external, is often erratic and unpredictable.

The most important tool used in diagnosing AM radio concern is a reliable weak AM signal source. A high-power AM Broadcast station one or two hundred miles away is ideal. The station should be clear enough so that you can understand what is being said with little or no difficulty. Another good weak signal source is a local station when the vehicle is in a poor reception area, such as under an overpass, bridge, or in a parking structure.

It is important to note that there are other sources of noise, external to the vehicle, that can interfere with the weak signal you are trying to receive. These external noises must be either taken into account or avoided. For example, power lines, transformers, fluorescent lights, electrical machinery, and traffic signal lights can radiate noise in the AM broadcast band. The increase of electrical and electronic appliances has made the noise level at many locations generally higher than in the past. It is best to test the concern vehicle in an area well clear of such noise sources.

Summary:

Select a set of test stations, especially the stations that may be the reason for the customer concern and some of which are over 100 miles away.


^ Note the reception performance of a known good vehicle in the desired locations. Note the presence of any local external noise sources (eg. power lines, etc.).

^ Compare the performance of the concern vehicle when receiving the test stations in the same locations.