MORE INFO - RADIO COMMUNICATIONS
On this page, you will find:
- More Fun Facts
- Understanding a Radio (ES, radio waves)
- How a radio works (AM, FM)
- More Devices that rely on Radio waves
- Radio Basic Components
- What is the Lifeline radio?
- Case Study: Mambo Elimu is changing the lives of child workers in Tanzania
- How Mambo Elimu works
- Helpful Links
- Click here if you want to go back to the first Radio page?
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UNDERSTANDING A RADIO
ELECTROMAGNETIC SPECTRUM
The EM is full of all different types of radiation, as: radio waves, infrared (meaning "below red," IR), visible light (only a small portion of this spectrum), ultraviolet light (meaning "above violet," UV), x-rays, and gamma rays. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X-rays and gamma-rays.
Check out the EM. Notice that it goes from lowest energy to the highest energy.
Click to make the picture larger: 
From NASA
On the left, you see waves that have the longest wavelength, lowest frequency and lowest energy. On the right, you see waves that have the highest wavelength, frequency and energy. Notice on the picture that as the wavelength size decreases, they increase in energy.
- Radio waves- These radio waves are the same kind of energy that radio stations emit into the air for your radio to capture your favorite tunes. Radio waves are also emitted by things as stars and gases in space.
- Microwaves- These waves cook and reheat your food. But, are also used in radar (to predict weather) or to transmit info (like phone calls and computer info) from one place to another.
- Infared light - You experience this everyday! These waves are the heat that you feel from sunlight or a fire.
- Visible light- This is the light you see! We see these waves as colors of a rainbow. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light.
- Ultraviolet (UV)- The sun, stars and other hot objects emit this light. The sun that burns our skin is UV light.
- X-rays - These are used by doctors to make pictures of your bones and teeth.
- Gamma waves - These have the most energy of any waves. These are used to kill cancer cells. Radioactive materials (like nuclear power plants) also emit these waves.
RADIO WAVES
Electromagnetic radiation with frequencies between about 10 kHz and 100 GHz are referred to as radio frequencies (RF).
Check out where the Radio Waves are on the electromagnetic spectrum. 
From Wikipedia
Radio frequencies include: (notice the names)
| Frequency | Range | |
| ELF | Extremely Low Frequency | 3 kHz - 30 kHz |
| LF | Low Frequency | 30 kHz - 300 kHz |
| MF | Medium Frequency | 300 kHz - 3 MHz |
| HF | High Frequency | 3 MHz - 30 MHz |
| VHF | Very High Frequency | 30 MHz - 300 Mhz |
| UHF | Ultra High Frequency | 300 MHz - 3 GHz |
| SHF | Super High Frequency | 3 GHz - 30 GHz |
| EHF | Extremely High Frequency | 30 GHz - 300 GHz |
Some examples of what things fall into certain frequencies.
From NASA
- HF - Long Range communications. Shipping, Aircraft, World Broadcast Communications, Radio Amateurs.
Prone to atmospheric changes causing fading and noise. Range from 500 to thousands of kilometers.
- VHF -
Medium range communications. Fleet vehicles, mobile, coastal shipping and air to tower communications. Range 70-100km (aircraft several hundred km).
- UHF - Police handheld radios, cell-phones, TV, and spacecraft to ground communications. In the high UHF range, the signal can "bounce" off buildings and reflect until it is detected by a receiver.
Radio frequencies are divided into groups that have similar characteristics, called "bands," such as "S-band," "X-band," etc. The bands are further divided into small ranges of frequencies called "channels." This is the frequency range assigned to them by the International Telecommunication Union (ITU). This organization divides the entire range of communications frequencies among those who use them. This includes commercial radio, television, and Amateur Radio.
For radio transmission, information is given to a carrier wave by varying (modulating) its amplitude, frequency, or duration.
Here are a few key terms that help explain how a radio works:
- Wavelength - The distance a wave travels through space in a single cycle. It can be measured from any point along the wave as long as it is consistently measured from the same point. Measured in meters (m).
- Amplitude- The strength, "loudness" or intensity of the wave. For radio frequencies, this quantity is commonly expressed as a power ratio in decibels (dB).
- Frequency- The measurement of the number of times that a repeated event occurs per unit time. Frequency of a radio wave is measured by the number of times in 1 second that the wave repeats itself (cycles per second). This is measured in hertz (Hz), named after Heinrich Hertz (see History- Timeline section). 1 Hz means that an event repeats once per second.
From: NASA.
- Modulation (modified) - Modulation allows the information that is sent over the radio waves to be understood at the other end. This process works by changing the amplitude or frequency.
Amplitude modulation (AM)
Technically, AM is a form of modulation in which the amplitude (strength) of a radio signal is varied in direct proportion to the modulating signal (this is different than FM- see below). The fact that radio signals can be decoded using very simple equipment is one of the primary advantages of AM. The main limitation is that it is susceptible to noise (it can’t sort out the difference between natural and man made noise and radio noise).
From NASA.
Frequency modulation (FM)
Technically, FM is a form of modulation in which the frequency of a radio signal is varied according to the modulating signal. FM is commonly used for high-fidelity music and speech broadcast, normal TV sounds and by VHS to record the black and white part of the video signal.
A few more DEVICES that rely on radio waves
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RADIO BASIC COMPONENTS
Any radio setup has two parts: a transmitter and receiver.
The transmitter, with the help of an antenna, takes a message, codes the information onto a sine wave and then transmits the signal. A receiver, with the help of an antenna then picks up the message on the sine wave, and decodes it.
WHAT IS THE LIFELINE RADIO? (This section was contributed by the Freeplay Foundation. )
The Lifeline radio is a wind up, solar-powered radio designed specifically for kids living on their own, for distance education and other humanitarian projects.
It is tough enough to work in the harshest of conditions and climates--it can stand sand and dirt. The Lifeline radio is rugged, colorful, easy to use, receives excellent AM/FM/SW reception and plays for many hours on wind-up energy or solar power.
Why is the Lifeline radio urgently needed?
In 2004, Children on the Brink a joint report of USAID and UNICEF reported that 42 million children in sub-Saharan Africa were orphans.
Children as young as ten years are heading households, caring for up to four younger children. These children are vulnerable and are often treated badly and have little or no means of support.
Many of these children live in extreme poverty and are unlikely to attend formal school on a regular basis. Very few will finish secondary school.
What is the Freeplay Foundation?
The Freeplay Foundation believes that education is the birthright of every child but over 100 million children in Africa are not able to go to school. The Freeplay Foundation provides Lifeline radios to ensure that children can have access to a good quality education by radio any time, anywhere.
Access to education and information helps children and other people in need to make the first step out of poverty. Radio can reach people in remote rural areas. But there is very little electricity in Africa and for the poor batteries to power radios are expensive and hard to come by Self-powered Lifeline radios solve this problem.
Case Study: Mambo Elimu is changing the lives of child workers in Tanzania
Tanzania is a desperately poor country where more than half the population lives in extreme poverty, surviving on less than US$1 per day. Over five million school age children have no access to primary education. An estimated 4.7 million are involved in economic activity and 300,000 children are engaged in the worst forms of child labor. From 1990 to 2000 the proportion of children working between the age10 -14 doubled from 23% to 46%. Children become farm workers, miners, domestic servants and sex workers, often under abusive and exploitive conditions. Thousands of children fall prey to child trafficking. Children working in mines and quarries are exposed to extreme danger and children working on tobacco, tea and coffee plantation are exposed to toxic pesticides. Education will give these children many more options and a more secure future.
However, Tanzania's overburdened formal school system cannot meet the needs of its out-of-school children. Funding cuts and teacher shortages are contributing to the rapidly deteriorating education system. Given the poor quality and difficult access to education, many parents have little incentive to send their children to school rather than send them to work.
Mambo Elimu, "education is everything" in Swahili, is a distance learning radio of the US-based Educational Development Center (EDC). Broadcast over the national radio station network, Mambo Elimu provides basic education to children aged 10-17 for grade levels one to four.
Tomaini, a tall handsome lad of 17 is teamed up with Grace, a shy 14-year-old. He left his mother and his village when his father died and joined his brother in the big city where he cooks chips and on a good day makes 50 cents with which he can buy some food and more potatoes to fry for his customers. Grace lives with an unemployed father and does domestic work for her uncle in return for food and board for her father and herself. Tomaini is proud to be learning English, a goal he never thought possible but although his name means “hope” he tell us he has very little hope for himself or his future.
 The boys in the back are Askari (guards) identified by the traditional red striped cloth. It is very unusual to see these young men in class. |
But children out of school, especially those who are orphans, need more than literacy and numeracy, so programs also include segments on, nutrition, hygiene, gardening, problem solving strategies, critical thinking processes and practical survival skills- like how to build and take care of a garden to grow food - to help children become successful members of society.
Most of the children live in poverty in isolated rural areas where there is no electricity and no money to buy batteries. The solar powered wind up Lifeline radio which can be heard by a class of up to 40 children has been requested to support the EDC program in remote informal schools and community centers to ensure access to Interactive Radio Instruction for those most in need.
grandmother dies. Jumaini hopes to use the math he is learning to be able to have his own shop one day and to make a lot of money.The Mambo Elimu distance learning program delivered by self powered Lifeline radio will ensure that children most at risk receive consistent high quality education and information. They will also receive information on dealing with health threats like YB and malaria and greater knowledge will keep them healthier.
Mambo Elimu classes have demonstrated a marked superiority over formal primary schools. In June 2004, in an inter-school exam between a primary school in the Iringa Rural district and a Mambo Elimu center, the top 13 scores were from the Mambo Elimu center.
Providing access to high quality, relevant education is the best way to eliminate child labor. It will empower children to resist hazardous, subsistence-wage employment. Improved education will lead to greater income security which brings improved health and family stability.
Who attends? |
Very poor children between 8 and 17 who would not normally be able to attend school. They are usually orphans, have parents who are too poor, or child laborers |
Where do they learn? |
Mambo Elimu centers which must have a supportive local community. Community centers and disused buildings (which must at least have a roof) can be used. Classrooms have benches but seldom desks. Children in government schools wear uniforms but Mambo Elimu students do not. |
How do they learn? |
Through Interactive Radio Instruction (IRI) - an imaginative use of stories, songs, physical activities and role plays that encourage and model interactive exchanges between teachers and students. |
What do they learn? |
Primary school curriculum grades 1 - 4 and valuable life skills are presented as an adventure as the children take a ride on the magic bus. |
Is there a teacher? |
Trained teachers are in short supply but the classes are facilitated by a literate adult mentor who is paid $1 a day to guide the children through the lessons. |
Does it work? |
In exams and tests, students from Mambo Elimu classes score higher than their counterparts in formal primary schools - even when up against their top performers! |
is from Mtwara in southern Tanzania. A domestic worker for an aunt and her two children, Sophia’s parents are learning disabled and unable to care for her. She said the best thing in her life is Mambo Elimu because she learns too much that helps her in her daily life. |
water. She and her sister share a mat and sleep on the floor in a rented room. Tatu aspires to make clothes for a living and enjoys learning about health, nutrition, and other subjects including English and math. - Freeplay Foundation
- Glossary of telecommunications terms
- History of radio
- History of radio
- Surfing the Aether
- USA's Federal Communications Commission (FCC) Radio Pioneers & Core Technologies
