Worksheet

Tracking a Weather Balloon: Voice or Data?

Grade 8 practice: use a weather club's radio range test and relay model to explain why digital signals carry information more reliably than analog ones.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS4-3

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1 NGSS standard
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10 questions
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Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Short answer

About this worksheet

What students practice

Students analyze range-test data to compare how noise affects analog and digital signals.
Students explain why checked and rebuilt digital messages are more reliable than analog voice.

How to use

Read the launch-day passage aloud, then have partners describe the pattern in each table column in words before answering. Use the open response as an exit ticket.

Curriculum

NGSS standard covered

MS-PS4-3

Explain why digital signals carry information more reliably than analog signals.

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Tracking a Weather Balloon: Voice or Data?

Compare analog voice radio and a digital tracker over distance.

Part 1: The range test

Read the passage and the range-test table, then answer the questions.

Finding the Payload

1The weather club at Ridgeview Middle School is getting ready to launch a high-altitude balloon. A small foam box called the payload hangs below the balloon and carries a camera and a GPS tracker. The balloon will rise about 30 km, burst in the thin air and drop the payload back to the ground on a parachute. It may land far from the launch site, so a chase team in two cars has to find it. The team plans to talk between cars with walkie-talkies, while the tracker in the payload radios its GPS position every 30 seconds.

2The two radios send information in different ways. The walkie-talkies use an analog signal: the radio wave changes smoothly to copy the shape of the speaker's sound wave. Any noise the signal picks up along the way changes that shape, and the listener hears it as hiss. The tracker uses a digital signal. Each position is sent as a short message of 0s and 1s, and every message ends with a check value worked out from the rest of the message. The receiving laptop works out the check value again. If the two do not match, the laptop throws the message away and waits for the next one.

3Club member Amara Oyelaran ran a range test along a long, straight reservoir a week before launch. She stayed at the boat ramp with a walkie-talkie and the laptop. Her teammate Joaquín rode with the club advisor to marked stops 1, 3, 5, 7 and 9 km down the shore road. At each stop, Joaquín read the same list of 40 words over the walkie-talkie, and Amara wrote down how many she understood. At the same stop, a spare tracker in the car sent 40 position messages. The laptop counted how many passed the check and whether it ever showed a wrong position. The team used the same radios, fresh batteries and the same antenna height at every stop.

4On launch day the payload may land behind a ridge, where the radios cannot reach the chase cars directly. The advisor plans to park a relay radio on the hilltop. A relay receives a signal and sends it on. An analog relay makes the signal it hears stronger and sends it again, hiss and all. A digital relay first decides whether each part of the message is a 0 or a 1, then sends out a fresh, clean copy of those 0s and 1s.

Amara's range test (40 words or messages at each stop)
Distance (km)	Words understood	Messages passing check
1	40	40
3	37	40
5	30	40
7	21	38
9	11	31

From the 1 km stop to the 9 km stop, the number of walkie-talkie words Amara understood dropped by words.

At the 9 km stop, what percent of the tracker's messages passed the check? %

Which statement best describes the pattern in the table?

A. Voice clarity fell at each stop, while the data stayed perfect through 5 km.
B. Voice clarity stayed steady until 7 km, then fell quickly at 9 km.
C. Both signals lost about the same amount at every stop down the road.
D. The data lost more than the voice did at each stop after 1 km.

The laptop showed 0 wrong positions at every stop, even at 9 km. Which explanation fits the passage best?

A. The tracker sends a stronger radio wave than a walkie-talkie does.
B. Damaged messages failed the check, so the laptop did not show them.
C. Digital radio waves pass through the air without picking up noise.
D. The laptop fixed the hiss in each damaged message before showing it.

Circle the two statements that are evidence that noise also affected the digital signal.

At 9 km, 9 of the 40 messages failed the check.At 1 km, Amara understood all 40 words.At 7 km, 2 messages did not pass the check.No wrong positions were shown at any stop.

Suppose Joaquín drove on to an 11 km stop and repeated the test. Based on the table, what is the most likely result?

A. All 40 messages passing again, since digital signals tend to recover with distance
B. About 11 words understood, since the voice stopped losing words after 9 km
C. Fewer than 11 words understood, fewer messages passing, still no wrong positions
D. Fewer than 11 words understood, and several wrong positions shown on the laptop

Part 2: Launch day and the hilltop relay

Use paragraphs 2 and 4 and the table to answer the questions.

A signal picks up some noise on its way to the hilltop relay and more noise on its way from the relay to the chase car. Which result does the model in paragraph 4 predict?

A. The analog relay removes the first hiss, so the voice arrives as clear as at the start.
B. The digital relay makes its copy stronger, so it sends the first noise on with it.
C. Both relays send on the first noise, so both signals arrive with the same damage.
D. The digital relay sends a clean copy, so the second noise is added to a fresh signal.

At the 9 km stop, 31 of every 40 messages passed the check. The tracker sends 120 messages each hour.

If the same rate held, about how many messages would pass the check in one hour? messages

The payload lands about 9 km from the chase cars. One teammate wants to read the landing position aloud over the walkie-talkie. Another wants to wait for the next tracker message. Which choice does the evidence support?

A. Wait for a tracker message, since any message shown has passed the check.
B. Read it aloud, since the voice got 40 out of 40 words through at 9 km.
C. Wait for a tracker message, since tracker radio waves travel faster than voice.
D. Read it aloud, since a voice message is sent faster than a data message.

10.

A new club member says, "The walkie-talkies are just as reliable as the tracker for sending the landing position." Write a claim, give evidence from the range-test table and explain your reasoning using what happens to noise in analog and digital signals.