Wireless communication and RF technology
Radio waves, antennas and the standards that enable wireless equipment to communicate
When a device sends data 'wirelessly', it exploits the fact that an electrical signal at a sufficiently high frequency can be radiated as an electromagnetic wave and picked up again far away—without a physical cable between. That field is called RF technology (high frequency, often abbreviated RF for radio frequency), and it's one of the four techniques—analog, RF, digital, and microcomputer technology—that the program's objectives explicitly mention you must be able to combine and troubleshoot.
§Frequency, wavelength and why it matters
An electromagnetic wave is characterized by its frequency — how many times per second it oscillates — and its wavelength which is inversely related to frequency: the higher the frequency the shorter the wavelength. Low frequencies travel far and penetrate obstacles well but can carry less data per second. High frequencies can carry large amounts of data quickly but are more easily dampened by walls and distance. The choice of frequency band is therefore always a compromise between range data amount and how much the equipment takes up.
§The antenna – the converter between cable and air
The antenna is the component that converts an electrical signal in a conductor to a radiated wave – and conversely captures a weak wave from the air and converts it to a small electrical signal the receiver can amplify. An antenna's size and shape are closely related to the wavelength it is designed for: as a rule of thumb, a well-functioning antenna is in a size order that matches the wavelength or a simple fraction of it. This is why an antenna for low frequency (long wavelength) is typically physically larger than an antenna for very high frequency.
§Wireless standards you encounter in practice
| Standard/teknik | Typical use |
|---|---|
| Wi-Fi | Wireless data network over short to medium distances |
| Bluetooth | Short-range connection between units, low power consumption |
| LoRa / low-energy IoT radio | Long distances, very little data, battery-powered sensors |
| Mobile network (4G/5G etc.) | Broadly covering data connection via telecom provider's master |
| RFID/NFC | Short-distance identification access card payment |
§Frequencies are a limited and regulated resource
The electromagnetic spectrum is a shared, limited resource — if two devices transmit on the same frequency in the same area at the same time, they interfere with each other. Therefore, the use of radio frequencies is regulated by the authorities; in Denmark, it is the Danish Energy Agency that administers the frequency plan and determines which frequency bands may be used for what and under what conditions. As an electrician, you need to know that a device that transmits wirelessly cannot just use any frequency — it must happen within approved bands and with equipment that complies with the current requirements.
§EMC — when equipment must be able to live side by side
Electromagnetic compatibility (EMC) deals with two things at the same time: that a device does not emit disturbances that bother other equipment nearby, and that it can itself tolerate the electromagnetic noise it will inevitably meet in the real world. A poorly shielded cable or an incorrectly sized antenna can make an otherwise well-functioning device into a source of disturbance for neighboring equipment — or conversely make it vulnerable to others' signals. EMC requirements are therefore a fixed part of the technical documentation and standards you as an electronics technician must be able to apply and relate to in your work.
- 01Know the difference between low and high frequency — and what each is good for
- 02Understand that an antenna is tuned to a specific wavelength
- 03Know that frequency use is regulated — not free play
- 04Think EMC from the start: both emission and immunity
“Wireless technology seems invisible — but it follows the same physical laws as all other electronics, just radiated through the air instead of a wire.”
— Professional view on HF technology.