Picture behind the story Hallands Län Grimeton Tjöloholmen

The alternator - the heart of the grimeton radio station

How do long waves actually occur?

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph.

Radiostation Grimeton

the only remaining machine transmitter in the world

Who still remembers the radios with their broadband reception, the transistors and the pointer, which comes to the right frequency by turning one of the round buttons and gets one of the worldwide stations depending on the choice? Previously, you had to press an option key for ultra-short wave, medium wave or long wave. For the first time, I think about how these waves are created at the Grimeton radio station in Sweden, in the only remaining machine transmitter in the world.

Basic knowledge of physics is definitely helpful for this article. Even those who once had an electrical kit as a child and made an electromagnet will be able to find their way into the technical description.

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph

Radiostation Grimeton

Of alternators and long waves

 

In addition to the huge, kilometer-long antenna system at the Grimeton radio station, there is a large, modern-looking machine hall at the heart of the system. Their architecture is somewhat reminiscent of that of hydropower plants. This is no coincidence, because one of the formerly two remarkable generators and many switch cabinets and pumps is waiting in the engine room of the Grimeton radio station. This is where the long waves from the longest wave transmitter Grimeton originate, which are sent around the world from here.

Somehow the inside of the machine house of the radio station Grimeton reminds me of films like “Back to the Future” or one or the other James Bond. The name of the most striking component of the system also contributes to this: the alternator.

Radiostation Grimeton and the Alternator

A monster made of 50 tons of cast steel

50 tons of cast steel and lots of copper – when this component is started up, it brings tears of emotion to the eyes, others awe and sweat.

All of this is not quiet, but this unit is the component that made international broadcasting possible in the first place. The alternator consists of a large drive motor that drives the high-frequency generator via a gear train.

The alternator can already be described as a great hell machine, the matt black appearance of which with the copper circular displays already makes a slightly wobbly impression. In the beginning there were two alternators that require a robust foundation.

The alternator is named after its inventor and designer, after Alexandersson.

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph
Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph

The drive motor of the alternator

The push for long waves

About ten times the household voltage is required to start the stator, the drive motor. With 2,200 volts, it brings the drive motor of the alternator to an output of 370 kilowatts, i.e. about 500 hp.

A real rarity of the stator is its two-phase winding. The stator draws its power from the neighboring transformer house of the Grimeton radio station, which is immediately visible next to the machine house.

In the Scott transformer installed here, the three-phase three-phase current is converted into two-phase three-phase current.

The drive motor runs at exactly 711.3 revolutions per minute and transfers its movement to the subsequent gear transmission, which then brings the generator to a constant 2,115 revolutions / minute.

The gear transmission

When one cog engages the other

The drive motor and alternator are connected to each other via a gear transmission. With the appropriate gear ratio, the alternator runs at a constant 2,115 revolutions per minute. This is the guarantee for the ideal frequency.

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph.

„The only remaining machine transmitter in the world. Once a year he broadcasts for Christmas "

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph

The high frequency generator

Use the viewfinder as a viewfinder

The high-frequency generator is a very idiosyncratic construction and may be reminiscent of a science fiction film from the 1960s. With its design, a very high frequency of 17,200 Hertz is achieved for rotating machines. In order to keep losses due to magnetic reversal as low as possible, the stator windings were built up in layers with thin-walled transformer sheet metal. The driven disk of the alternator has a thickness of 7.5 mm and a diameter of 1.60 m. In comparison: a car sheet is about 0.8 mm thick.

The steel disc looks like a gearwheel, but to minimize air resistance, the gaps between the teeth have been filled with non-magnetic brass.

The stator surrounds the rotating steel disc and is only a maximum of one millimeter apart. There are 64 armature windings around the steel disc on the stator. These armature windings act as an electromagnet, but as I said, a millimeter apart.

Now the steel disc rotates at 2,115 revolutions / minute, in the area of ​​the steel teeth a strong magnetic field is created by the electromagnetic coils. But this is interrupted again and again between the teeth of the steel disc by the brass fillings.

Current flows in each armature winding with 30 amps at a voltage of 100 volts. This current is passed on to the transformers of the high-frequency signal box.

It is best to imagine a large gear, which rotates quickly. Maybe someone still remembers the wheel of fortune on a TV show of the same name. You just hold a sheet of metal to your teeth. This makes noises as often as the sheet metal strip is touched by a tooth. At 2,115 revolutions, this happens so often that there is a constant beating noise at intervals of milliseconds. This frequency can be compared to the frequency.

In nominal terms, the high-frequency generator as it is available in the Grimeton radio station can achieve 200 KW. For normal telegram operation in the USA, however, 80 KW was generally sufficient. The readability of the signals was guaranteed here.

The liquid resistances

Electricity that goes through the water

The drive motor and alternator are connected to each other via a gear transmission. With the appropriate gear ratio, the alternator runs at a constant 2,115 revolutions per minute. This is the guarantee for the ideal frequency.

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph
Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph

The multiple antennas

Like orphaned electricity pylons

The transmitter system consists of six mutiple antennas with a distance of 380 meters. Each of these masts is 127 meters high. At the top are the 48-meter-wide cross arms. There is a coil in front of each antenna mast.

Under the antenna mast there is another network of appropriate wires in the ground.

The connecting cables now run from the nacelle to the antennas, which are now connected to each other by the 12 antenna wires. The magnetic field, which is generated by the high-frequency generator, now flows in the copper antenna wires, each 2.2 kilometers long. The vibrations are now so strong that they reach New York and can be read there.

Maybe the whole thing can be compared to a wave pool, only that the pool is a thousand kilometers long. You create the water waves on one side. they have to be strong enough to reach 1000 kilometers away. If the waves arrive too weak, you have to generate them stronger at the beginning.

With long waves or long waves, they now come through the air not as water waves but as electromagnetic waves.

The receiving station of the Grimeton radio station

About the 13-kilometer antenna

Sending telegrams to America was one thing, but the news from America also had to be received. This also required antennas, which, however, only had to absorb the vibrations that were generated in the transmitting station near New York. These antennas were correspondingly smaller and more reminiscent of power lines that are carried on wooden poles.

The two parallel antenna wires had a total length of 13.4 kilometers and ran across Kungsbacka to the transformer to Skärsjön, about 40 kilometers north of Grimeton. From here, the signals were forwarded to the Kungsbacka receiving station.

Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph
Grimeton Sverige, Langwellen, Kodak Tri X, Leica M Elmarit 2.8 28 asph

And why Hertz has nothing to do with the heart

But what does Hertz have to do with frequency?

The gear between the electromagnetic coils generates vibrations at a higher speed of the gear. From a certain number of vibrations / second, electrical signals radiate into the room. The art of radio waves, which are also called frequencies (number of vibrations / second).

In order to be able to distinguish the messages sent, each station now worked with a different frequency. And the frequencies for radio, telegrams, telephones and television must also differ from each other.

By the way, Hertz is the unit for one frequency, named after its discoverer Heinrich Hertz, who introduced the first radio transmission.

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