by Alexia Alexandria

Created on: June 15, 2008

Unlike frequency modulation (FM) which involves the variance in frequency of a signal to convey information, AM, or amplitude modulation, works by varying the amplitude, or strength, of the signal in accordance to the information being sent. Because it is susceptible to interference from electric devices and atmosphere, it is not the dominant form of broadcasting and is mainly used for talk and news programming.

4 SOURCES OF INTERFERENCE & BAD RECEPTION

Antenna System
The length of an antenna affects signal strength. The higher the antenna is, the stronger the received signal strength. As the height of an antenna decreases, so does the signal strength. Some radios have an internal antenna and cannot be adjusted.

Building
Walls made of cement, aluminum, and brick decrease signal strength. This is because it is hard for AM radio waves to pass through these materials.

Weather
When the weather is clear, radio waves are able to capture radio stations that are farther, but this does not mean that reception of local stations are clearer. Distant stations can interfere with the local stations.

Appliances and Devices
Domestic appliances such as hair dryers, food mixers, and vacuum cleaners can cause interference because they are operated by electric motors. They tend to cause buzzing and whining when they are in use. Refrigerators and swimming pools interfere by causing harsh buzzing because they are operated by a thermostat. Washing machines and dryers cause 'clicks' and pops' in the radio receiver because they are operated by switches. Televisions, power lines, and computers cause harsh buzzing in the radio receiver because they are operated by electricity.

SOME TIPS TO IMPROVE AM RECEPTION
Opening the windows and placing the radio near a window in a building made of cement, aluminum, and brick.

If the antenna is adjustable, moving it around and increasing its height both can improve reception. If the radio has an internal antenna, placing the radio in a high place and positioning it in different areas of the room until the reception clears may also have an effect

You can minimize interference from other devices by not placing the radio near a domestic appliance when either it is in use. Also, you can find the source of the buzzing if you have a portable radio by moving it around to hear when the buzzing becomes harsher. If any region of the radio faces the source of interference, it will affect reception so rotating the radio can improve reception.

If the radio is plugged in, overturning the plug can polarize it. If the radio is battery operated, putting in new batteries may help

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