This document discusses radio communication technologies. It explains that radio uses radio waves to communicate over long distances. It describes how modulation works by adding digital or analog sound waves to a carrier wave. It distinguishes between AM and FM modulation and their characteristics. The document also outlines the basic components and process of radio signal transmission from a transmitter to a receiver via antennas, including modulation, amplification and demodulation. It provides examples of radio stations in Madrid.
4. • KEY CONCEPT
· Radio is the technology that uses radio waves to communicate. They are the
biggest wavelenght waves in the electromagnetic spectrum, which makes them
suitable for transmission over long distances.
· It is used in radio communication, radar, remote sensing, radio navigation and
multiple other applications. We will focus on radio communication in this chapter.
5. • MODULATION AND CARRIER WAVE
· Modulation is a process in which a digital or analogue sound wave is added to a
basic radio wave (called carrier wave) for it to travel faster and further.
· A carrier wave (or carrier signal) is an electromagnetic wave at a steady (fix)
frequency and amplitude on which information can be imposed.
6. • AM AND FM MODULATION
· AM modulation adds the information from the input wave by changing the
amplitude of the carrier wave. The frequency remains the same.
· FM modulation adds the information from the input wave by changing the
frequency of the carrier wave. The amplitude remains the same.
· Digital modulation alters
the carrier wave’s frequency.
7. • AM AND FM COMPARED
FM AM
Frequency Higher (88 to 108 MHZ) Lower (54 to 1600 kHz)
Interference due to physical
obstacles
More prone Less prone (bigger wavelength)
Interference or noise due to
electrical phenomena
Less prone (the weakest
signal is eliminated by the
receiver)
More prone (two signals
received at the same frequency
are demodulated)
Distance Travels closer Travels further (bigger
wavelength)
Bandwidth Bigger Smaller
Price More expensive (complex
circuits, more repeaters needed)
Cheaper (simpler circuits and
equipment)
Sound quality Better (more bandwidth, less
interference)
Worse
8. • HOW SIGNAL TRAVELS
· Radio waves are generated by an electronic device called transmitter that is
connected to an antenna which radiates the waves. The receiver is connected to
another antenna that allows it to receive the signal.
· When a device is able to both generate and receive radio signals, it’s called a
transceiver.
9. · The microphone transforms the
sound waves into electrical impulses.
· The oscilator generates the fixed
frequency carrier wave.
· The modulator combines the
waves and inputs a modulated AM
or FM signal.
· An amplifier increases the energy
of the wave so it can be sent to the
broadcast antenna.
· The broadcast antenna generates
radio waves that travel through
space.
Broadcast antenna
Amplifier
• TRANSMITTER
Turner
circuit
10. · The receiver antenna picks up all
the frequency waves.
· The turner circuit selects the
wished frequency (radio station).
· The demodulator separates the
carrier wave from the original input
signal.
· The amplifier increases the energy
of the input wave.
· The loudspeaker converts the input
electromagnetic wave into a sound
wave, making it hearable.
Broadcast antenna
Amplifier
• RECEIVER
Receiver antenna
Turner
circuit
