Who needs metal when you're surrounded by water? Mitsubishi has announced a rather quirky new way to transmit and receive data, by creating what it claims is the first ever working antenna to be made out of seawater. Seawater, being salty, is conductive: In fact it's about 1000 times more conductive than the water that you drink. That means that, in theory at least, it can be used as a rudimentary antenna. They are, after all, just pieces of conducting metal whose shape and size are designed to reliably receive or transmit radio waves.
That's in theory. In practice, seawater is much, much less conductive than most metals — by a factor of about one million. So when Mitsubishi decided to give the seawater aerial — or SeaAerial as it calls it — a stab, it embarked on some theoretical calculations first. Having established the optimal diameter of a water jet required, it gave it a try.
In practice, the device uses a pump and nozzle to create a finely tuned jet of seawater which is aimed into the sky. The result is an aerial with an efficiency of 70 per cent, which it claims is enough to transmit or receive signals. In a small scale model, the company's shown that the SeaAerial can reliably pick up a TV signal.
But it has bigger hopes for the technology. It points out that very low frequency signals — the kinds used by war ships and submarines to communicate over huge distances at sea, say — require correspondingly large aerials which are tens of metres tall. In situations where it's difficult or impractical to install such a device, Mitsubishi suggests a water jet could be used. We'll have to wait and see if that's just a pipe dream.