![]() An un-modulated FM wave might look like:Īnd a modulated FM radio wave has higher and lower frequencies indicating higher and lower audio frequencies in the signal:įrom left to right, we have the normal, un-modulated wave, then the lower frequency wave (representing lower audio amplitudes), then the higher frequency wave (representing higher audio amplitudes). The F in FM comes from Frequency - defined by how quickly the wave vibrates every second. The audio signal is the wave on the top, with the corresponding Amplitude Modulated wave below it.Įxample two: FM radio. An un-modulated AM wave might look like:Īnd a modulated AM radio wave has higher and lower energy (amplitude) waves indicating higher and lower audio frequencies in the signal:įrom left to right, we have the normal, un-modulated wave, then the lower amplitude wave (representing low points in audio waves), then the higher amplitude wave (representing crests or high points in audio waves).Ī more detailed version of an AM signal is below: The A in AM comes from Amplitude - the energy or strength of the signal, operating at a single frequency. The type of modulation is what makes them different.Įxample one: AM radio. In the two examples below - AM and FM radio - the M stands for modulation. ![]() There are many types of modulation, and different technologies can use one or more types to send and receive information. A wireless signal needs to be modulated-or changed-to send information. In addition to having different frequencies, wireless signals can be different in the way they convey information. Cellular phones: 850MHz, 1900MHz, and others.Television: Many frequencies from 470MHz to 800MHz, and others.Cellular phones use many different frequencies. Broadcast transmitters for AM, FM and Television use frequencies below 1000 MHz, Wi-Fi uses two bands at higher frequencies - 2.4 and 5GHz. One thousand Megahertz is one Gigahertz.īelow we can see the span of frequencies that are commonly used in communications. As an example, FM radio signals vibrate around 100 million times every second! Since communications signals are often very high in frequency, we abbreviate the measurements for the frequencies - millions of vibrations a second is Megahertz (MHz), and billions of vibrations a second is Gigahertz (GHz). Frequency is measured in Hertz, which is the count of how quickly a signal changes every second. If the signal vibrates very quickly, it has a high frequency. If the signal vibrates very slowly, it has a low frequency. These are some of the most common signals, but what makes them different?įirst of all, wireless signals occupy a spectrum, or wide range, of frequencies: the rate at which a signal vibrates. You may be familiar with AM and FM radio, Television, Cellular phones, Wi-Fi, Satellite signals such as GPS and television, two-way radio, and Bluetooth. There are many, many types of wireless technologies. These waves can travel some distance depending on the strength of that energy.įor more on how electromagnetic signals work, check the #External Resources section at the end of this document. These are formed when electric energy travels through a piece of metal - for example a wire or antenna - and waves are formed around that piece of metal. Wireless signals are electromagnetic waves travelling through the air. Wireless signals are important because they can transfer information - audio, video, our voices, data - without the use of wires, and that makes them very useful. Working through the activities, or diving deeper into the subject with a group may take longer. Reading through this material should take about an hour. Antennas - how the type of antenna changes the way the router broadcasts.Power and Receiver sensitivity - how far each wireless device can go, and how well a router can listen and filter out interference and noise.Wi-Fi Signals - the unique characteristics of Wi-Fi, and how signals are organized.Wi-Fi Modes - how networks are made up of clients, access points, or ad-hoc devices.Wireless devices - the differences and uses for receivers and transmitters.Wireless signals - what they are and how signals can differ.In addition to some background information, this document covers six basic concepts: Reading and working through Learn Networking Basics before this document will help you with some of the concepts used in wireless networks. While wireless networks can be just as fast and powerful as wired networks, they do have some drawbacks. We use it for networking because it is cheaper and more flexible than running cables. ![]() Wireless technology is used in many types of communication. This document covers the basics of how wireless technology works, and how it is used to create networks.
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