The Physics of an AM Radio :: Physics Radio Papers

The Physics of an AM Radio It’s was a beautiful sunny morning and Bill just kissed his wife goodbye and headed out the door on his way to work. As Bill got into his car he realized that he missed the Utah Jazz game the night before because of a late business meeting and fell asleep before the news came on so he couldn’t catch the highlights or even the score. He remembered that he could catch the rundown on AM frequency 930 (Sports News Radio). Many people enjoy listening to AM radio because of how convenient it is to listen and catch up on the sports, weather or just enjoy the entertainment of listen to Rush or Dr. Laura, but are much like Bill and don’t have any idea how the signal that carries these programs is sent or even received. In an attempt to understand this process, Bill confronts a part time employee who is currently studying electronics and has a basic knowledge of how the AM radio found his car or even his home works. Almost all AM radios work under the same basic design. There are two very simple yet very important things that make AM radio possible. What are these things? A transmitter(the station) and a receiver(the radio). THE TRANSMITTER Each radio station that desires to have a frequency(signal) on AM radio must notify the FCC and are assigned a frequency that they can use to send their information out on. The very first part of the transmitter is a quartz crystal. This is used because it is very stable and efficient which is important because there are certain laws and guidelines that the stations must abide by. They cannot go over or below the assigned frequency by more than 5K hertz, making a bandwidth of 10K hertz. After the quartz crystal, is an oscillator where the actual physics of the transmitter comes in. The oscillator is made up of a variety of electronics components including an operational amplifier and a combination of resistors and capacitors. Resistors are defined as-The impedance to the flow of electric current. The resistance is equal to the voltage across the object divided by the current through it. Measured in volts per ampere, or ohms.(Physics, A World View 513) Current is defined as-A flow of electric charge. Measured in amperes. (Physics, A World View 513) A combination of a resistor and capacitor in series or parallel is called a filter.