we call radio wave a class of electromagnetic radiation whose frequency is included in what we call the radio spectrum ranging from frequency 0 to 300 gigahertz. From that frequency we have already started talking about infrared, visible, ultraviolet...
Electromagnetic field is a wave process similar to when you throw a stone into a pond and a wave is formed that has highs and lows (peaks and valleys) and varies. In the same way, even if we don't see it, the electromagnetic field varies; it has values that are first higher, then are lower and so on, undulating.
, and what is frequency? Frequency has to do with how quickly that wave ripples, that is, how fast it goes from a maximum to a minimum or how closely the highs and lows are in time because the important thing to keep in mind is that that value varies. At the time between highs or lows, that is, between values that are repeated, we call it period. And the inverse of the period, how many turns to that cycle we have given per second we call the frequency and are measured in hertz (which are neither more nor less than cycles per second). For example, if I have a period of 0.1 seconds it means that in a second I have found 10 peaks. If we think of a bus that goes around a circuit we can say that the bus period is one hour or we can say the laps that the bus gives in an hour, the laps that the bus gives is the frequency and the time it takes to take a walk is the period.
The frequency of a wave, that is, how quickly it makes those variations, it will change its characteristics, its behavior. And because we are able to generate waves of different frequencies, that allows us to organize the spectrum. It allows us to decide, for example, that when we generate a 900 megahertz wave we use it for mobile telephony, or a 2.4 gigahertz wave we use it for wifi. They're all radio waves, but with different frequencies,
The frequency of a wave, that is, how quickly it makes those variations, it will change its characteristics, its behavior. And since we are able to generate waves of different frequencies, that allows us to organize the spectrum
We use them for all types of wireless communications and we also use them for communication over the cable. But the most popular use is that of wireless: television, communications with mobile, the data that the mobile sends or receives or how we communicate with the wifi, the FM radio..., all that goes by radio waves and reaches us because a receiver with an antenna is capable to receive the information and transfer it to us,
What we wanted to convey: image, sound, etc., has first been converted to a format suitable for transmission, which is usually a digital format; that information in digital format is transported in the radio wave and when it reaches the receiver, the bits carried by the wave become what they were at the beginning: image or sound,
Radio communications started out as analog. Then it was sent as the information. If I speak to a microphone, the voice produces variations of a current and that is what was used to modify the radio wave and was transmitted directly through the antenna. That voice is now bit-encoded for transmitting because the digitized information is much more robust.
, how is that information transmitted within the radio wave? We have to change some wave feature depending on the message you want to send. The easiest thing to understand is that you change the amplitude. The radio wave has an amplitude that increases and decreases between two possible values. I can change those values, make them bigger or smaller, according to the information I want to send. We call that modulation, we modulate the wave with the information we want it to transport. If I want to send 1, 2, 3; i command a wave that has first amplitude 1, then amplitude 2 and then amplitude 3. And when it reaches the receiver, the receiver will look at the amplitude and it will say: 1, 2, 3. But instead of being 1, 2, 3 can be someone's voice or bits that encode any information. Changing its characteristics the radio wave transports me along the distance the information that I want,
We also use radio waves to heat food inside the microwave. They are the same as those of the wifi what happens is that inside the microwave we put more power than the one that we transmit through the air, because we don't want to warm people, do we? And it is that certain frequencies can make the molecules of the water resonate and that they heat up,
Radio waves also serve to see beyond what our human capabilities allow, for example the radar we can know what we have around even if it is very far, or even hidden. Light is also an electromagnetic wave but of specific frequencies that we see and we generally do not call them radio waves, but we talk about visible frequencies. But just like i do with light I capture images with a camera, with radio waves from other frequencies I can capture images through walls or through our body,