Understanding Amplitude Modulation for Radios

[MadmanMurray]

I'm learning about radios at the moment but there's a few things I'm not clear about concerning modulation. I'll use audio amplitude modulation as an example. Let's say I have a device which I speak into and this device converts the variations of the sounds waves coming outta my mouth into an electrical signal which varies in amplitude in a wire. This wire is attached to an antenna which converts the electrical signal into a radio signal.

Is everything I described there amplitude modulation or am I missing something? I keep reading about 2 signals being merged and that there's a difference between the modulating signal and the carrier signal. Is the carrier signal a separate signal of the desired frequency? For example if my sound converting device converts my sound waves into an electrical signal which varies in amplitude would the frequency be varying and chaotic meaning I would need to merge it with a carrier signal of fixed frequency? Is that the general idea?

 

[jtbell]

Does the following help?

http://hyperphysics.phy-astr.gsu.edu/Hbase/audio/bcast.html#c3

 

[sir-pinski]

Yes, everything you described is a form of amplitude modulation. However, there are a few key components that are missing in your explanation that are important to understand.

First, let's define amplitude modulation (AM) as a method of transmitting a radio signal by varying the amplitude of the carrier wave in response to the modulating signal. In simpler terms, the modulating signal (in this case, your voice) is used to vary the strength or height of the carrier wave, which is then transmitted through the antenna as a radio signal.

Now, let's break down the components you mentioned. The first is the device that converts your voice into an electrical signal. This is known as a microphone. The microphone takes the variations in air pressure (your voice) and converts them into corresponding variations in electrical current.

Next, you mentioned a wire that is attached to the antenna. This wire is known as a transmission line and it carries the electrical signal from the microphone to the antenna.

The antenna is responsible for converting the electrical signal into a radio signal that can be transmitted through the air. The antenna also helps to shape and direct the radio signal.

Now, let's talk about the carrier signal. The carrier signal is a separate signal of a fixed frequency that is used to carry the modulating signal. This is necessary because without a carrier signal, the modulating signal would not be able to travel very far. The carrier signal provides a stable and consistent base for the modulating signal to be transmitted on.

In AM, the carrier signal is modulated by the modulating signal. This means that the strength or amplitude of the carrier signal is varied in response to the modulating signal. This is what creates the variations in the height or strength of the radio signal, which can then be received and decoded by a radio receiver.

So, in summary, AM involves a modulating signal (your voice) being used to vary the amplitude of a carrier signal (of fixed frequency) which is then transmitted through an antenna as a radio signal. This signal can then be received and decoded by a radio receiver. I hope this helps clarify any confusion you may have had about amplitude modulation. Keep learning and exploring the fascinating world of radios!