A demonstration of a crystal radio - Part 1

This video demonstrates a crystal radio similar to that used in the early days of broadcasting.

Crystal sets are powered from the signal being received - no batteries or amplifiers are used.

The incoming station comes via a wire antenna (not shown) and is selected by a tuned circuit.

A tuned circuit comprises a coil of wire and a variable capacitor. Moving the variable capacitor knob changes the station.

A diode detector converts the radio frequency signal from the tuned circuit (which we can't hear) to a sound signal that we can hear through headphones.

As crystal sets are self-powered, signals on them are often weak and they might not receive all signals that a more sensitive radio would.

Several stations were heard on the set demonstrated but only a couple were loud enough for this demonstration without an amplifier.

The stations with the time pips were the ABC about 40 kilometres away. The later stronger station with the news bulletin was 3MP, about 20 kilmetres distant. Other stations were heard in the headphones but background noise was too high for them to be picked up by the camera. The antenna was about 20 metres of wire.

If you want to build one, crystal set circuits are readily available on the web. A search will reveal both simple and fairly complex designs, with performance varying accordingly.

Part 2 follows with the improved signals obtainable with a better antenna and altered coupling into the receiver.

Category:

Science & Technology

Tags:

• crystal
• set
• radio
• AM
• broadcast
• tuning
• receiver
• signals
• antenna
• earth
• diode
• detector
• capacitor

[vk3ye]

@okrustyone not 3AW - for some reason it's the weakest AM station here and a struggle on a crystal set. 3AW's sister station, 3MP, is the strongest followed by the ABC stations.

[ajboomboom5]

whats the power output from the radio? i want to try this but with a thousand radios =/

[vk3ye]

I don't know but it would be in the microwatts region. It would be better to have fewer high efficiency crystal sets - some have been able to get them to drive speaker and there should be details on the web.

[vk3ye]

Yep high impedence phones. I couldn't find them when I did Part 2 so I used a rocking armature telephone earpiece instead. Not quite as high impedance as the headphones but still good volume possible.

[lostsound2001]

cool chip .it's what I call real old school...Peace Old Hippie

[MrDaytonShaw]

do they still sell them???

[jamesabout]

The ear plugs for a crystal set can be found on ebay. I bought a pack of 5 or about eight dollars delivered to my mailbox. How good is that.

[va4cqd]

@picaticatara

less coil higher freq

[picaticatara]

Would more or less coil get you to a higher frequency?

[jsjassem]

good job man

[renekenshin6573]

High impedance headphones or crystal earphones are quiet rare so most enthusiast attach audio matching transformers on the output

[Ilovemyoldguitar]

What heppened to the focus? I thought my monitor was on the way out.

[okrustyone]

3AW Melbourne.