At that speed, a beam of light could go around the Earth at the equator more then 7 times in a second. The reason that it takes so long for radio messages to travel in space is that space is mind-bogglingly big.
The distances to be traveled are so great that even light or radio waves take a while getting there. It takes around eight minutes for radio waves to travel from the Earth to the Sun, and four years to get from here to the nearest star.
How long does it take for transmissions to get between DS1 and Earth? Each time the signal is amplified , the noise is also amplified. Gradually, the signal becomes less and less like the original signal. Eventually, it may be impossible to make out the music in a radio broadcast against the background noise, for example. Noise also adds extra random information to digital signals. However, this noise is usually lower in amplitude than the amplitude of the ON states.
As a result, the electronics in the amplifiers can ignore the noise and it does not get passed along. This means that the quality of the signal is maintained, which is one reason why television broadcasters have changed from analogue to digital and radio broadcasters are in the process of changing. You drive through a tunnel, and the music stops. Radio, whether satellite or over the air, is transmitted as a signal that is interpreted by your device.
In the following activities, we will learn more about the features of digital and analog signals by simulating how these two types of signals are transmitted and used to store information. Digital and analog signals are transmitted through electromagnetic waves. Changes in frequency and amplitude create the music you listen to or images that you see on a screen. Analog signals are composed of continuous waves that can have any values for frequency and amplitude.
These waves are smooth and curved. Digital signals, on the other hand, are composed of precise values of 1s and 0s. Digital waves have a step-like appearance.
Analog signals are prone to distortion because even slight errors in amplitude or frequency of the wave will change the original signal. Digital signals are a more reliable form of transmitting information because an error in the amplitude or frequency value would have to be very large in order to cause a jump to a different value. These two signal types are used to communicate and send information in many different forms, like radio transmission, text messages, phone calls, streaming videos, and playing video games.
They also can be used to store information and data. Data storage is used by large companies like banks to store records. Individuals also use data storage for personal use, like storing files, photos, games scores, and much more. This activity models the key differences between digital and analog signals in their resolution and signal fidelity.
Students will perform two simulations: one simulating multiple transmissions of an analog signal, and one simulating multiple transmissions of a digital signal. Analog images are composed of rounded lines to represent that analog waves can have infinite values. Digital images are composed of straight lines that follow the grids on the handout representing how digital signals are composed of quantized values. Arrange students in groups of five. Credit: Andrea LaRosa At each table, give each student a different analog alien page.
Hold the digital versions until later. There are five different alien drawings. Each group should have one of each of the five types of aliens. The students should not show their aliens to one another.
After the students complete the analog round of drawings, give each student the digital version of the same alien they started with the first time. Communication Signal Simulation Student Directions We are going to simulate the sharing of a message over time and distance. This activity requires passing a paper from person to person, having each person replicate a drawing on it, then passing it onto the next person at your table.
Passing the paper and replicating the drawing simulate the time and space over which signals travel. Student making one copy of the alien image. Credit: Andrea LaRosa After the two minutes, fold the original alien image behind the paper so that only your new drawing can be seen. Pass your paper to your left. Each paper pass represents the message traveling over time and distance. In the grid immediately to the right of the redrawn alien, use a pen or marker to redraw the alien image you can see to the best of your ability.
Do not erase or correct your drawing. You will be given two minutes to complete your drawing. Fold the alien image you copied behind the paper so that only your new drawing can be seen.
Repeat steps until the alien you originally drew returns to you. Analyze the progression of initial image to the last drawing. Record your observations in the Student Observation Sheet. Repeat the entire simulation again with the digital round alien images.
Student-generated progression of alien drawings. Credit: Andrea LaRosa Be sure to analyze the progression of initial image to the last drawing. Unfold your alien drawings and observe the images drawn during the activity. Identify and describe the similarities and differences between the two images.
Identify and describe what changed during each drawing. Support your choice with evidence from the activity. Teacher Note: In the digital round simulation, the alien images are composed of straight lines that follow the grids on the handout representing how digital signals are composed of quantized , or a limited number of values.
In this activity, students will familiarize themselves with characteristics of digital and analog signals, and apply their characterization to choosing digital or analog storage for a specific example. Which type of signal would you suggest to record a highly-detailed song of an endangered bird?
Support your choice with evidence from your card sort. Students will act as digital-analog converters to decode binary pulses, and to create a picture by changing the pulses into colored pixels.
The music transmitted to your car via satellite radio and the information stored in data libraries are both digital signals that use a binary system.
In a binary system, there are only two digits, 1 and 0. The value or meaning of these digits can vary. Following the binary code will guide the path to take on a logic map, and help in finding the intended colors.
This will code for the color green. Digital signals are transmitted to computers in the form of electronic signals sent as pulses. The image below is an example of a digitized wave. If we were to use each group of three numbers to find a corresponding color on the table above, we would use:.
Most electronics like smartphones, computers, and television screens use liquid crystal display LCD technology. The screen is made of millions of tiny pieces called pixels. The electronic device receives coded information, in the form of digital signals, and uses electricity to control the color of the pixels.
Each tiny pixel is simply changing from one color to the next depending on the electrical signal, but since the pixels are so small your eye detects movement in the overall image. Each student is assigned a digital wave graph like the one pictured below. Using the logic gate map, students will decode the signal into the pixel colors for part of the mosaic. To make your own classroom mosaic masterpiece, four classes complete a panel of a larger Post-it mural.
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