Learning Resources
Lesson
Functional components of radio systems
There are two major parts in a radio system—a transmitter and a receiver. An AM radio is used below as an example.
The AM radio transmitter has several major components, illustrated by the diagram
The power supply is the source of electrical energy for the transmitter. The RF (radio frequency) Oscillator generates the carrier wave at a fixed radio frequency (for example 640 kHz). Input is an amplifier that takes the information from a source such as a microphone, CD Player, or computer and processes it so that it can be added to the carrier wave. The RF amplifier combines the carrier and the information signal, boosts the power and sends it to the antenna. The energy from the RF amplifier to the antenna creates an electromagnetic wave which is the radio transmission.
The AM radio receiver also has several major components, illustrated by the diagram
The antenna receives the signal from the transmitter. The RF amplifier boosts the signal. The local oscillator creates a carrier wave exactly like the incoming one. The Mixer combines the incoming signal with that from the local oscillator in order to remove the carrier wave from the incoming signal. The information signal is then exactly the same as that which came from the Input block (microphone, etc) in the transmitter. The information signal is then amplified to drive the speaker.
Other types of radio have different components, depending on how the signals are produced and modulated, but the same principles apply.
Two-way radio includes both a transmitter and a receiver as part of the device. Cell phones, HAM radios and CB radios are two-way radio systems with transmitters and receivers in the same device.
Types of radio
Radio is divided into various bands of frequencies. The common bands are
Frequency Range (Bandwidth) |
Frequency Designation |
Frequency Range Used for |
| 535-1605 kHz (kilohertz) | MF (medium frequency) | AM Radio |
| 1800 kHz-20MHz | Shortwave | Shortwave Radio |
| 27 MHz (megahertz) | HF (high frequency) | CB Radio |
| 30-50 MHz | VHF (very high frequency) | Police and Fire |
| 50-54 MHz | VHF | Amateur Radio |
| 54-216 MHz | VHF | TV channels 2-13 |
| 88-108 MHz | VHF | FM Radio |
| 110-136 MHz | VHF | Aircraft Radio |
| 137-156 MHz | VHF | Public Service and Amateur Bands |
| 156-176 MHz | VHF | Marine Radio |
| 470-890 MHz | UHF (ultra high frequency) | TV channels 14-83 |
| 824-894 MHz | UHF | Cell phones |
| 914-928 MHz | UHF | Portable telephones |
| 1.3-1.6 gHz (gigahertz) | UHF | Radar |
| 2.4 GHz | UHF | Portable telephones |
Marine radio uses in Canada include includes telephone, high seas telephone, Navtex (GPS satellites), pollution reports, satellite phones, and radiomedical. There are dedicated frequencies for weather and distress.
Aviation Radio uses include air traffic control, GPS, navigation communications and communication beacons.
For a more detailed description of how radio works, including some simple activities to illustrate radio transmission, go to
Be sure to follow the full article. There is a list of parts at the top and bottom of the page, and a next page link at the bottom
Activity
Assigned activities
Develop a profile of a typical cell phone system. Create a presentation in a format specified by your instructor
- the cell
- general function of the cell
- receive and transmit frequencies
- cell phone range
As a starting point for information go to
Test Yourself
There is no self test for this lesson.