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💎 The Radio Treasure Hunt

Name     Class     Date  

How to hunt the Treasure

Listen to the beeps. The Treasure sends out three separate signals: a loud one, a medium one and a quiet one. The closer you get, the more of them your Hound can hear — and the faster it beeps.

Watch the screen. The screen fills up from the bottom: count the lit rows, from 0 to 5. The more rows, the stronger the signal, so they rise as you get closer. If the screen goes blank but you can still hear beeping, keep going — the sound reaches further than the screen can measure.

Turn your body. The Hound's aerial listens in every direction at once. That sounds helpful, but it means the Hound can never tell you which way the Treasure is — only how strong the signal is. There is no arrow to follow.

Luckily you can fix that yourself. Radio waves do not travel through a person easily, so if you stand between your Hound and the Treasure, you get in the way and the reading drops. Turn slowly on the spot and watch for the reading to dip. When it dips, the Treasure is behind you.

An aerial that listens all around equally is called omnidirectional. You can buy aerials that listen mostly one way instead — a bit like cupping your hand behind your ear — and people who do this as a sport carry one so it points straight at the Treasure. Your micro:bit has the all-round kind built in, so your own body is the tool you use instead.

Use the sunglasses trick. When every bar is lit and nothing changes as you move, press button A. Press button B to undo it. Part 3 explains why this works.

Before you start: what do you think?

As you walk away from the Treasure, what will happen to the number of bars on the screen? Tick one.

☐  They will go down slowly and evenly, one bar at a time.    ☐  They will stay high, then drop suddenly.    ☐  They will not change.

Why do you think that?

Part 1 — Does the signal get weaker with distance?

First press button B. That puts the Hound back to normal in case anyone has pressed A, which would make every reading too low.

Stand at each marked distance from the Treasure. Wait for the reading to settle, then count the lit rows on the screen — a number from 0 to 5, not the number of little red dots.

Take three readings at each distance. The signal wobbles, so one reading on its own cannot be trusted. To find the middle one, put your three numbers in order from smallest to biggest and use the one in the middle — so 3, 5, 4 becomes 3, 4, 5, and the middle is 4.

Now draw a line graph of your middle values. Put a cross for each distance, then join the crosses.

Describe the shape of your graph. Did the signal fade evenly, or did it drop faster in some places than others?

Was there a distance where the screen went blank but you could still hear beeping? If so, where?

Part 2 — Can the signal be blocked or bounced?

2a. Blocking

Stand still, about 8 m from the Treasure, holding the Hound in front of you. Turn slowly all the way round, watching the bars.

When was the reading lowest? Explain what your body was doing to the signal.

A human body is mostly water, and water soaks up this kind of radio wave. Trackers use this deliberately: turn until the reading dips, and the Treasure is behind you. It is the only way to get a direction out of an aerial that listens all around it.

2b. Bouncing

Take a reading 8 m from the Treasure out in the open. Then take another 8 m from the Treasure but standing close to a wall or fence. Keep everything else the same — same distance, same person, same way of holding it.

Were the two readings the same? Radio waves can bounce off hard surfaces, so near a wall the Hound may pick up the signal twice — once straight from the Treasure and once after a bounce. What did you find?

Only one thing changed between those two readings. What was it, and why does that matter?

Part 3 — When the meter runs out of room

Press button B first so the Hound is back to normal. Then walk to about 2 m from the Treasure. All 5 rows should be lit. Now step 1 m closer.

What happened to the bars?

Here is the problem. You are very close, but the screen looks exactly the same whether you are 2 m away or right on top of it. Why can the screen not show you the difference?

Press A once and step back and forth. Record what you see.

The important question. When you press A, does the Treasure's signal actually get weaker? Explain your answer.

Think about putting on sunglasses. Does the sun get dimmer, or does something else change?

Part 4 — What did you find out?

Finish these sentences using your own results.

As I moved further from the Treasure, the signal…

When something solid got in the way, the signal…

When all the bars were lit, the Hound could not… so I…

Which of your measurements do you trust least, and why?

Challenge — real data from this project

These are genuine measurements taken outdoors on 6 September 2026, using the same equipment you have been using. Signal strength is in dBm: a number closer to zero means a stronger signal, so −52 is much stronger than −87. The last three columns show how many of 75 packets arrived from each of the Treasure's three beacons.

Plot signal strength against distance on the grid below.

1. Between which two distances does the signal drop the most?
2. The quiet beacon disappears somewhere between 3 m and 8 m. Why does the quiet beacon vanish before the loud one?
3. The tricky one. Look at 15 m and 20 m. The signal at 20 m is stronger, even though it is further away. The scientists who took these readings checked, and it was not a mistake. Using what you learned in Part 2b, suggest why this might happen.