Ruri Rocks (瑠璃の宝石)

Later!

See ya!

Let's see, what to do once I get home?

First thing's first. Ice cream!

Must be the Suoh Shrine's summer festival.

Grandpa took you when you were little. Don't you remember?

He did?

You climbed up onto the sacred boulder.

It was a whole fiasco.

No way. I don't remember that.

Well that's disappointing.

I bet Grandpa's shaking his head somewhere.

Hey, that reminds me.

Didn't you say that Grandpa used to collect rocks?

He had all sorts of junk piled up in the storage room.

Really?! Do we still have them?

Hmm... I'm not sure.

We probably tossed them.

What?! Can I borrow the keys? Lemme go check!

It's so dusty in here.

But I might find quartz.

Or something even more rare.

That box smells like treasure.

Ouch...

What's this thing?

Suoh Tanigawa?

I dunno, but I found two rocks inside.

Memories Come with Rocks and Noise

Memories Come with Rocks and Noise

Along with copper wire and a coil, it looks like.

I think it was my grandpa's, since the box is labeled "Tanigawa."

I wonder what this card is.

'Sup?

What's that box?

That's the thing, we don't know!

But we're guessing it's related to rocks.

Did you switch up your hobbies or something?

I thought you were into stuff like jewelry and makeup.

I still am.

I just like this stuff now, too.

Huh.

Lemme see.

Shoot, something rolled away!

Found it.

S-Sorry, did I break it?

I dunno.

I'm not even sure if it was working in the first place.

Oh.

Hmm... Maybe Nagi-san would know.

It's a crystal radio.

You don't see these every day.

And it doesn't look commercial.

Is it homemade?

Hold on, Nagi-san. How can you tell?

Well, it's obvious if you look at the coil and detector.

What else could it be?

That bundle of copper wire you've got is the antenna.

And this is the ground.

Self-made ones are rare to come by nowadays.

Looks like it was made sometime after World War II.

Nowadays?

Have you guys ever heard of them?

They used to be popular as magazine freebies.

Crystal radios came with magazines?

By radio, you mean that radio, right?

That's right.

B-But... It's so bare looking.

Actually, it's pretty old, but it looks like all the parts are here.

But where do you put the batteries?

Seto-san, what a great question!

Crystal radios don't require batteries.

Circuit Layout of Crystal Radios

Antenna

Earth (Ground)

Coils

Condenser

Detector

Earphone

The radio waves themselves carry energy,

so, it just converts that energy into sound.

First, the antenna and ground, or the aerial circuit, pick up the radio waves.

Aerial Circuit

Then, the coils and condenser, or the tuning circuit, select the signal.

Tuning Circuit

Detection Circuit

Finally, the detector, or detection circuit, extracts the audio signal.

When a mineral is used as the detector, it's called a crystal radio.

Crystals are used here!!

Th-That was a bit hard to follow.

So the mineral...

Converts radio waves into sound.

I don't really get it, but it's cool!

Ruri, did this radio come with any earphones?

Earphones?

Yeah. Radio signals received through crystal radios

aren't strong enough to output through a normal speaker.

So it should require special earphones.

I don't think so...

We can't listen to it without them?

No worries!

I've got one right here!

Modern standard earphones usually have

Rochelle Salt Crystal Earphone

Corrugation

Rochelle salt oscillator

Aluminum diaphragm

Armature

Support rubber

Standard Earphone

Magnet

Diaphragm

Coil

an impedance or electrical resistance of 20–30 ohms,

but crystal radios require earphones with several thousand ohms.

That's why we use this crystal earphone made with Rochelle salt.

Impe—what? Who's Rochelle?

In other words, crystal earphones can convert even weak signals into sound.

Yeah, but this coil is pretty worn down.

You're probably better off building a new one.

Coil... Then I'll be able to listen to it?

Yup, I think so.

I wanna hear what it sounds like!

Me, too!

Great, then let's gather materials.

But Arato-senpai.

Don't you need to compile that data by next week?

Bus Stop Maeshiba University Front Gate Kanetsu Transport

Arato-san seemed pretty busy.

And Imari-san has a report due, too.

They were nice enough to tell us everything we need, but...

What should we do?

Do you want to wait until they can help us?

Enameled wire

Sandpaper

Plastic wrap tube

Safety pin

Brass plate

Let me think...

Good luck!!

Seto-san, are you free after school tomorrow?

Do you think we can fix it ourselves?

Yeah, let's do it!

Enameled wire, sandpaper, a safety pin...

What's the difference between enameled wire and tinned copper wire?

Does that have to do with the resistance thing?

What is that, anyway?

I'm not sure... Maybe how bendable it is?

Huh? What are you two doing here?

Well, since I broke it and all...

You were looking for parts?

Yeah. Not that I had any clue what I was looking for.

If you wanted to help us, just say so!

Huh? Help you?

Yeah. That's what you were up to!

Oh well. Fine, why not?

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Introduction to Crystal Radios

Learn How to Make Radios and Electric Circuits

History of Radio Broadcasting

Learn from the Basics

with Illustrations!

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Electric Circuits

It looks sort of...

Ugly.

Did we miss a step?

Hear anything?

Not a peep!

That's weird.

The antenna receives radio waves, and then the coil and condenser select the frequency.

The detector converts the radio waves of that frequency into sound,

which should get picked up by the earphone.

How about now?

Nope, nothing.

I don't hear anything either. We must have made a mistake.

There should be radio waves floating all around here.

My arms hurt.

Not a bad job.

Yeah, you did great.

If you can't hear anything after connecting the antenna and the ground,

there might be something wrong with the detector.

You mean this?

This is pegmatite.

You can't use these as detectors.

Pegmatite

Many minerals used in crystal detectors have a metallic luster.

Pegmatite is a type of granite that forms as magma cools and solidifies.

Quartz

Mica

It's made up of coarse-grained minerals like feldspar, quartz, and mica.

Feldspar

I think you can find some near the shrine close to town.

Is something wrong?

Why was it in here if it's not even usable?

Did Grandpa screw up, too?

What exactly are detectors anyway?

It's different from tuning, right?

That would be the coil's role.

I remember! The coils aren't batteries.

Voltage