A View from John Pavlus
Navy Antenna Using Seawater instead of Metal
The Electrolytic Fluid Antenna has a range of 30 miles and could be used on sea or land.
The average U.S. Navy vessel has 80 different antennae bristling out of it like a spiny beetle. But it’s often hard to find adequate space for all of them without interference, and their height can expose the ship to radar detection. What if they could be replaced using something a ship always has plenty of: seawater?
Daniel Tam, an engineer at Spawar Systems Center (sort of a DARPA for the Navy), exploited the magnetic induction properties of salt water to create an electrolytic fluid antenna which can broadcast and receive VHF and UHF signals.
The design is simple: just shoot a thin stream of seawater through an electromagnetic coil called a current probe, and presto – instant radio communication. A jet 6 feet tall will operate on VHF, and 2 feet gets you UHF. Current probes can be easily stacked and installed anywhere on the deck, because the water-streams can simply be turned off when they’re not in use.
The tech makes sense on land, as well – especially for restoring emergency communications in a crisis area whose power grid has been knocked out. Dump rock salt into a bucket of fresh water, foot-pump it through some plastic pipe with small solar- or generator-powered current probe, and flood victims or emergency-response personnel could be on the air much faster.
The fluid antenna’s range has been successfully tested at 30 miles, and the Navy is seeking commercial partners for the patent-pending technology. Expect neo-survivalist types to start stockpiling these babies faster than you can say “peak oil”.