說到無線電天線，大家第一時間想到的或許都是金屬與電線。但如果說有人用水做出了天線，你信還是不信呢？2016年1月底，三菱電機（Mitsubishi Electric Corporation）向大家展示了通過將海水陣列噴到空氣中來創建無線電收發天線的SeaAerial技術。這種設計據說是世界上首個能夠接收數字地面電視廣播的海水天線，適用于在海上或沿著海岸線部署。

在日常生活中，我們與之打交道的無線電頻段相對強勁卻很短，因而設備中的收發天線可以做到很微小。

不過隨著無線電頻率的變長、以及信號的衰弱，所需要的天線就長的多了，然而也這意味著打造此等規模的天線會非常昂貴、耗時、且難以搬運。

另一方面，如果可以把水當做材料，就可以輕松泵出“日內瓦大噴泉”（Geneva's Jet d'Eau）這等規模的天線了。

當需要搬動的時候，只需關閥斷水，將電氣組件搬到另一個地方即可。不過，為什么海水可以、純水就不行了呢？顯然，這與它們的導電能力有關。

純水不含雜質，因此極難導電。但是海水中溶解有各種礦物離子，所以被當做是最方便、實用、完美的SeaAerial材料。

當然，海水部分并不是SeaAerial的重點。美國海軍近年來對它產生了濃厚的興趣，只是目前仍限于保持住躍出水面的噴灑裝置，以免底部海水“短路”并影響到信號。

該公司稱，噴嘴里面是一個用絕緣材料制成的1/4波長管，用以物理上隔絕周水和保持電路。SeaAerial設計的另一個要點是，雖然鹽水可以導電、但畢竟還是比金屬小很多。

換言之，海水天線的“效率”要比金屬天線低得多。三菱稱，通過運行計算機模擬，確定了理想的柱直徑可讓效率增加70%。

目前三菱正在嘗試其他類型的新型天線材料（導電液體），并申請將SeaAerial作為注冊商標。

[編譯自：Gizmag , 來源：Mitsubishi]

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Mitsubishi's SeaAerial turns fountains into antennae

Mitsubishi's SeaAeriel could be used to create a water aerial tens of meters high, as illustrated by Geneva's Jet d"eau (Credit: Shutterstock).

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.