Which materials can absorb a signal?

Radio technology (basics)

There is hardly an area where we can do without the wireless transmission of voice and data. Regardless of whether television, radio, mobile communications or computer networks. Radio technology is part of our lives everywhere. Radio technology allows us to transmit data wirelessly over the air.

What seems so common to us is associated with various physical effects and complicated and sensitive technology. The physical processes are shown in the following in a simplified manner for an understandable explanation.

What is radio technology?

Heinrich Hertz was the first to demonstrate how electrical and magnetic fields can be used to transmit messages. Back then, in 1886, there were no electron tubes or transistors. Therefore, the transmission signal was generated by means of a spark gap. It was only later found out that the range of the signals, the radio waves, can be increased with long wires. The spark gap died out, the antenna was born, the name Funk stayed. And that is why every technical device that uses electrical and magnetic fields to transmit data or communication is assigned to radio technology.

What is an antenna?

By definition, an antenna is a transmitting and receiving device for electromagnetic waves. Strictly speaking, an antenna is a metallic transducer for an electromagnetic wave between a line and free space. Antennas receive electromagnetic waves and send or radiate them. The antenna is connected like a two-pole. The principle structure is, however, a four-pole, whereby two poles have no fixed physical connection. Instead, they hang in the open.

How are radio waves generated?

Radio waves do not arise by themselves. A vibration generator is necessary to generate radio waves. This can be an oscillator that generates the so-called fundamental or carrier wave. It is a physical effect. In electronics, however, one does not usually speak of waves. Because radio waves are frequencies.
The oscillator generates an alternating voltage signal with a certain frequency. From a certain number of oscillations per second (frequency), electrical signals tend to radiate into free space. Frequencies (f) are given in the unit Hertz, or Hz for short. Heinrich Hertz serves as the namesake here.

What is the carrier frequency all about?

The carrier frequency generated by the oscillator is not yet any information. The information must first be piggybacked on the carrier frequency in the form of a different frequency. Only then can information, usually different states in coded form, be transmitted. These processes are called modulation. The best known modulation methods are amplitude modulation (AM), phase modulation (PM) and frequency modulation (FM). The frequency modulation is z. B. used in the transmission of analog FM radio stations.

How was that again with vibration and frequency?

The number of oscillations, i.e. radio waves per second, is specified as frequency (f) with the unit Hertz (Hz).

in Hz in sec.

Example: 16,000 oscillations per second are 16,000 Hz or 16 kHz.

How far does a transmitted signal go?

The range of a signal depends on the wavelength of a frequency and the signal strength. And, to be precise, the cushioning too. The signal strength is determined by the transmission power. The wavelength l is given in meters. The following formula applies for this:

The speed of light is a constant. The value is 300,000,000 m / s (meters per second) or 300,000 km / s (kilometers per second).
The above formula results in different wavelengths from the frequencies. Assuming that the transmission power is constant, the wavelength determines the range. This means that with constant transmission power, the range of the transmitter decreases proportionally to the wavelength. If you halve the wavelength, the range decreases drastically. The higher a frequency, the shorter the range.

According to general knowledge, the range of radio signals is smaller, the higher the frequency range in which the radio is being used. However, this only applies if the radio signals are emitted omnidirectionally or in sectors. This is how it was done for all cellular technologies up to 5G.
The situation is completely different when using directional antennas. Here the behavior is reversed: the radio signal gets better with the same transmission power with a higher frequency and has a longer range.
Technically, one speaks of guided radio relay signals. To do this, however, you still have to research the frequency range between 95 GHz and 3 THz.

Can a signal be sent on one frequency just like that?

No, you can't. In order to avoid frequency chaos, frequencies or frequency ranges are assigned to an application. E.g. for radio, television, amateur radio, CB radio, aircraft radio, ship radio, taxi, police, fire brigade, mobile radio, etc. Radio technology is very advanced. So far that the free space is even used as a transmission medium for local networks. And because the transmission medium is available practically free of charge, it is used with great pleasure and a lot. The density of the radio systems is so high that interference-free operation is only possible through the legally prescribed distances between the frequency ranges.

Attenuation of radio waves

Unfortunately, radio waves have the disadvantage that they get weaker with range. This means that radio waves do not have an infinite range. Radio waves are attenuated by objects. Depending on the material properties and composition of the obstacles, there are different damping properties.

WoodlowFurniture, ceilings, partitions
plasterlowPartition walls without metal grille
GlasslowWindow panes
watermediumHumans, moist materials, aquarium
BricksmediumWalls, ceilings
concretehighmassive walls, steel-reinforced concrete walls
plasterhighPartitions with metal mesh
metal very high Elevator shaft, fire doors, reinforced concrete structures

The following negative effects arise in the context of radio transmission:

  • Absorption: signal is swallowed
  • Reflection: the signal is reflected back
  • Refraction: Signal is diverted in a different direction
  • Scattering: signal distribution

The stability and speed of a radio connection have to do with the range of the signal and the disruptive properties in the room. The shorter the range, the less interference can affect the signal and the higher the transmission speed can be. The higher the range, the more interference there is on the way between the transmitter and receiver. This results in disconnections and long connection times. Cable transfers tend to be faster and more stable.

How safe is radio technology?

The signal emitted into free space can be overheard by anyone who is within range of the signal or who can receive it. There is a risk that an attacker not only listens to the signal, but changes it and sends it again. Radio systems that cannot handle manipulated signals have significant security deficiencies.

Basic terms in radio technology

In the context of radio technology, there are many different terms that are frequently used, behind which mostly complex physical effects are hidden.

Future of radio technology

The future of radio technology is characterized by a shortage of frequencies and the constantly increasing need for higher transmission rates. For this reason, various methods for increasing capacities and data rates in mobile radio networks play a major role in research and development in mobile communications.

Basics of radio technology

Overview: radio technologies and radio systems

Other related topics:

Product recommendations

Everything you need to know about communication technology.

Communication technology primer

The communication technology primer is a book about the basics of communication technology, transmission technology, networks, radio technology, mobile communications, broadband technology and Voice over IP.

I want that!

Everything you need to know about communication technology.

Communication technology primer

The communication technology primer is a book about the basics of communication technology, transmission technology, networks, radio technology, mobile communications, broadband technology and Voice over IP.

I want that!