MIT Physics Demo -- Telegraph Transmitter

A solenoid enclosed in another solenoid is connected to a 12 volt battery. Also contained in the circuit is an iron contact switch connected to a spring arm, with a gap on one side of it. When the circuit is closed, the inner solenoid attracts the iron switch across the small gap. This breaks the circuit, making the switch move back to its original position, which closes the circuit again. Thus, the switch moves back and forth quickly, causing oscillations of high voltage in the outer solenoi
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A solenoid enclosed in another solenoid is connected to a 12 volt battery. Also contained in the circuit is an iron contact switch connected to a spring arm, with a gap on one side of it. When the circuit is closed, the inner solenoid attracts the iron switch across the small gap. This breaks the circuit, making the switch move back to its original position, which closes the circuit again. Thus, the switch moves back and forth quickly, causing oscillations of high voltage in the outer solenoid. This high voltage causes sparks to jump the large gap between the ends of the outer solenoid.

These sparks cause electromagnetic radiation, which is how telegraphs were originally transmitted wirelessly. Morse code can be transmitted by opening and closing the power source.

This specific transmitter was made by the Marconi company, and is very much like the telegraph machine that would have been used on the Titanic. Read more about spark gap transmitters here - http://en.wikipedia.org/wiki/Spark_gap_transmitter

See the original post on MIT TechTV - http://techtv.mit.edu/videos/845

Category:

Education

Tags:

• mit
• mittechtv
• physics
• demonstration
• demo
• telegraph
• wireless
• telegraphy
• transmitter
• electromagnetic
• radiation
• spark
• gap

[BirdValiant]

The FCC probably hates this experiment.

[marsCubed]

If everyone had one of those we wouldn't need cell phones.

[Mandragore12345]

a coil within another coil.... (mutual) induction

[MasterTxJ]

@MasterTxJ Allthough you might not want to enter your backyard without rubber boots.

[MasterTxJ]

You could probably light up your whole backyard with one of these babies. If you ground the pulsed current it could be transmitted through the ground to LED's with rectifiers and capacitors, which would light up in an area perhaps 10 meters in radius. Perhaps? Maybe you wont even need the rectifiers since it's pulsed DC induction?

[Thetruthishere11]

just an iron core wrapped with wire attached to magnet which open and closes circuit.

[benjwgarner]

@BirdValiant These things have been illegal for high-power transmitting since 1921 because they bleed harmonic interference all over the radio spectrum.

[msf60khz]

For good RF generation you need a much smaller gap and the balls need to be polished. This is what Heinrich Hertz found.

[kdc43]

OK, while you at it, give me a back massage.

[Necrokutan]

Please let me beat you now.

[Joelduffy]

Eh, the interference probably doesn't project that far. It's not a freaking lightning storm. ;)

[Poparotzi]

ITS ALIVE!!!!!