When someone mentions a radio aerial, it tends to conjure up a vision of something made of steel and wire. But what about one made of water? On Thursday, the Mitsubishi Electric Corporation unveiled its SeaAerial, which uses a column of seawater sprayed into the air to create a radio transceiver antenna. Designed for use at sea or along shorelines, it's billed as the world's first seawater antenna capable of receiving digital terrestrial broadcasts.
In our day to day lives, we're used to dealing with radio frequencies that are so short and relatively strong that the transceiver antennae on our devices are correspondingly tiny. However, as radio frequencies get longer and the signals become weaker, the antenna has to be longer as well.
This fact of life means that many radio installations require very large antennae that are expensive, time consuming to build, and far from portable. On the other hand, if an antenna could be made out of water, you could have an aerial the size of Geneva's Jet d'Eau in the time it takes to fire up the pump. When it came time to move the installation, it would simply a matter of switching off the water and moving the electronics to another location.
But why seawater and not garden variety fresh water? Contrary to popular belief, pure water is a very poor conductor of electricity. It's the mineral ions dissolved in it that actually carry current, so for practical purposes, seawater works best for making a watery antenna.
The point about the SeaAerial isn't that it's aquatic. This isn't the first seawater antenna – the US Navy has taken a keen interest in the idea in recent years, but so far it's been limited by the necessity of keeping the plume-spraying apparatus out of the water to prevent the circuit from grounding in the sea and killing the signal. Mitsubishi's innovation is an insulated nozzle that transmits the radio signal to the saltwater plume. According to the company, inside the nozzle is a quarter-wavelength tube of insulated material that physically separates the plume from the surrounding water and maintains the circuit.
Another factor in the SeaAerial design is that, though saltwater can conduct electricity, it is much less conductive than metals, which translates into poor efficiency as an antenna material. Mitsubishi claims that by running computer simulations it was able to determine the ideal plume diameter – allowing for a 70 percent increase in efficiency.
Mitsubishi is currently working on other conductive and transmutative liquids as new antenna materials and has applied to register SeaAerial as a trademark.Source: Mitsubishi
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