CQ DE H2O

November 9, 2010 10:18 AM

Liquid antenna turns sea water into signal. "The US Navy has created a device which turns a jet of sea water into an impromptu liquid antenna, creating a powerful, high frequency broadcast tower for ships, emergency situations and easy transportation."

U.S. Navy announcement via SPAWAR.

Also on Wired blog.

posted by mykescipark (42 comments total)

...I just figured out a cheap and disgusting way to fix all those iPhone signal problems.
posted by griphus at 10:20 AM on November 9, 2010 [13 favorites]

So, after deafening the planet's whales, they now plan on going after the birds?
posted by mrstrotsky at 10:21 AM on November 9, 2010 [4 favorites]

Someone should tell them about tin foil.
posted by bondcliff at 10:22 AM on November 9, 2010

creating a powerful, high frequency broadcast tower for ships, emergency situations and easy transportation.

Not to mention jamming device, which is what they are going to use it for right off the bat. A little HERF'ng to get the games started.
posted by Old'n'Busted at 10:24 AM on November 9, 2010 [1 favorite]

I wonder if they've been testing it near LA with missile launch frequencies.
posted by MCMikeNamara at 10:24 AM on November 9, 2010

Weird. I took a piss yesterday and I swear I got Radio 4.
posted by MuffinMan at 10:24 AM on November 9, 2010 [8 favorites]

emergency situations

No. Wind^*. Reliability in an emergency is critical. You don't want your PLB or ship beacon not to work because gail force winds are blowing your antenna apart.

^*(can't watch vid at work---doe they mention wind effects?)
posted by bonehead at 10:25 AM on November 9, 2010 [1 favorite]

(or even Hurricane Gail-force winds. Stupid homonyms.)
posted by bonehead at 10:29 AM on November 9, 2010 [1 favorite]

I had a girlfriend named Gail Force; she was the weather reporter for the Georgia Straight.
posted by PareidoliaticBoy at 10:35 AM on November 9, 2010 [4 favorites]

Public water fountains + free wifi?

And now people have reasons to hang out at the park again...
posted by yeloson at 10:37 AM on November 9, 2010

And now people have reasons to hang out at the park again...

Other than the hand jobs. Oh, I've said too much.
posted by The 10th Regiment of Foot at 10:42 AM on November 9, 2010 [7 favorites]

So I know that they're going to patent this, but any idea on where an avid experimenter could acquire one of these "metal donuts" and what material is best?
posted by arimathea at 10:45 AM on November 9, 2010

Everything I want to say just can't be said out loud. I just wonder if this will be shared with the public or kept for defense use only? It could be a game changer in the unwired backwoods of the developing world.
posted by The Lady is a designer at 10:46 AM on November 9, 2010 [2 favorites]

They "jumped the shark" when they started talking about non-maritime uses. A piece of wire is far more stable and much easier to deal with than jumping column of water with corrosive salts saturated in it.

A fluorescent light bulb makes a more attractive improvised antenna, anyway.

If you're not concerned about eye safety, ionizing oxygen in the atmosphere can make for an even more extreme antenna.
posted by MikeWarot at 10:49 AM on November 9, 2010

Heh. I saw the YouTube video demonstrating this on Twitter a couple of days ago and thought this might make the blue. It's fascinating that this works. I actually thought about posting it myself, but then I got too busy arguing with people about Henry Rollins...
posted by limeonaire at 10:50 AM on November 9, 2010

I know this may be a little kookie, but why can't they just turn those big metal tubs they ride around in into a big antenna in a pinch?
posted by The 10th Regiment of Foot at 10:51 AM on November 9, 2010

Other than the hand jobs. Oh, I've said too much.

Well, that could be a horrifying mashup between improv everywhere and chat roulette...
posted by yeloson at 10:53 AM on November 9, 2010 [1 favorite]

The 10th Regiment of Foot: Antennas are slightly more complicated than just using any old metal material you have at hand.

Also, the Navy is very keen on hiding/controlling the existing magnetic signatures of their ships.
posted by Loto at 10:56 AM on November 9, 2010 [1 favorite]

U.S. Navy announcement via SPAWAR.

What a coincidence: "SpaWar" is the working title of the TV reality show I'm developing.
posted by ZenMasterThis at 10:58 AM on November 9, 2010 [1 favorite]

So NOW is it the future? Or does this need to come with a flying battleship?
posted by SpacemanStix at 11:08 AM on November 9, 2010 [1 favorite]

It could be a game changer in the unwired backwoods of the developing world.

If I lived there, I wouldn't want to waste valuable potable water on being able to download tweets.

Well, maybe to read Metafilter, but only in emergencies.
posted by Blazecock Pileon at 11:15 AM on November 9, 2010

Since when did seawater become potable ?
posted by The Lady is a designer at 11:17 AM on November 9, 2010 [1 favorite]

Well, if you're in the backwoods, you most likely don't have an easy source of seawater. Not in the woods around here, anyway.
posted by echo target at 11:18 AM on November 9, 2010 [1 favorite]

This is such a simple and brilliant idea, I can't think why somebody didn't think of it years ago. There's very few inventions that inspire those kinds of thoughts, and this is one. I'm quite thunderstruck by the fact that, in 2010, somebody can still say something as simple as 'use a jet of seawater as an antenna' and have it be so instantly, self-evident and useful and yet and at the same time so totally new to one's personal experience.
posted by Dreadnought at 11:19 AM on November 9, 2010

If you don't have access to seawater you have to add salt to fresh water for this to work, thus making it difficult to render it potable again.
posted by Loto at 11:19 AM on November 9, 2010 [2 favorites]

I was thinking of "backwoods" as in "boondocks" of technology - islands in the Pacific, tsunami affected South East Asia, earthquake challenged Haiti... no shortage of salty unpotable water but critical need for communication no?
posted by The Lady is a designer at 11:26 AM on November 9, 2010 [2 favorites]

I know this may be a little kookie, but why can't they just turn those big metal tubs they ride around in into a big antenna in a pinch?

Contrary to conventional wisdom (a la wrap some tinfoil around the rabbit ears) antennae work best when they resonate at or near the desired frequency.

It is similar in function to the sympathetic response in glassware to an opera singer's high C - the more resonant the glassware at that frequency, the easier it is to break.

Very very simply, an ideal antenna are some fraction of the wavelength(s) meant to be recieved, 1/2 wave and 1/4 wave working best, but for multimode antennae there is a whole subset of engineering devoted towards optimizing performance. Wikipedia has a nice overview, although I spent two semesters in college only barely scratching the surface of this subfield of electrical engineering.

Simply put, you can't just hook up a chunk of metal to a receiver and expect magic to happen. If it's too big, you need too much power to make it resonate. If it's too small, it won't at all.
posted by Pogo_Fuzzybutt at 11:26 AM on November 9, 2010 [3 favorites]

Plus, depending on the height of the stream of water, you can get UHF, VHF and HF broadcasts, all from the same jet of H2O. You can even set up multiple jets of water, at different heights, to broadcast on different bands simultaneously.

I'm imagining that something like this could be really useful for submarines as a way to maintain a completely concealed presence, only using water as different antenna to maintain radio communication.

But then, I'm also imagining someone watching this as it goes by and the multiple jets looking like the Bellagio fountain had taken a vacation in the mid-Atlantic.
posted by quin at 11:29 AM on November 9, 2010 [2 favorites]

Other than the hand jobs. Oh, I've said too much.
posted by The 10th Regiment of Foot

Flagged as insufficiently eponysterical.
posted by sebastienbailard at 11:54 AM on November 9, 2010 [4 favorites]

yea, i have a salt water aquarium and we are hooking the antenna up right now, but did anyone warn us with- "don't try this at home"?
posted by tustinrick at 11:54 AM on November 9, 2010

I've been throwing chunks of metal in the air since 1979 and talked across the oceans with them... almost anything works, and the length is a bit critical, but not the end of the world.

A pair of metal tape measures hooked up to a balun can give you a 1/2 wave diapole, or any other combination you care to think of, quickly.
posted by MikeWarot at 11:54 AM on November 9, 2010 [1 favorite]

no shortage of salty unpotable water but critical need for communication no?

So we're looking for places with radio equipment, electrical power for the equipment and for the saltwater jet, but no antennas.
posted by atrazine at 12:11 PM on November 9, 2010 [2 favorites]

So now, in future hollywood depictions of warfare, to communication-ally isolate a ship requires them scraping all the regular antennas off the hull AND running out of water. Won't someone think of the poor trope's we're killing?!?

More seriously, I wonder if they could use these antenna underwater by encapsulating them in jets of cavitation air.

But then, I'm also imagining someone watching this as it goes by and the multiple jets looking like the Bellagio fountain had taken a vacation in the mid-Atlantic.

Who is the Bellagio talking to NOW?
posted by nomisxid at 12:19 PM on November 9, 2010

If I lived there, I wouldn't want to waste valuable potable water on being able to download tweets.

Potable water not only isn't necessary, it's completely wrong, Blazecock Pileon.

So we're looking for places with radio equipment, electrical power for the equipment and for the saltwater jet, but no antennas.

Ever tried to build a hurricane-proof radio tower, atrazine? OK, this won't work during the hurricane, but it will work after. Also good on boats, where all of the above are present, and tall antennae are a bitch.
posted by IAmBroom at 1:35 PM on November 9, 2010 [1 favorite]

If you don't have access to seawater you have to add salt to fresh water for this to work, thus making it difficult to render it potable again.

You would need a ton of salt though, since it's a jet of water. Which means the water would either need to be recycled (not exactly easy) or something else.

I wonder, though if you could just use a trough of water.

I wonder if they could use these antenna underwater by encapsulating them in jets of cavitation air.

Uh, why? Most radio waves can't get through much water, so there wouldn't be much point in broadcasting underwater in the first place.
posted by delmoi at 1:40 PM on November 9, 2010

So we're looking for places with radio equipment, electrical power for the equipment and for the saltwater jet, but no antennas.

Could one of these newfangled mobile phones do this?
posted by The Lady is a designer at 2:21 PM on November 9, 2010

Ha, funny, our electrical engineering manager at work has been suggesting this very thing for a while now. We make underwater robots, and the otherwise hydrodynamic, nothing-protruding-that-can-break torpedo shape of the robot is really marred by the 17" antenna sticking out the top of it. This would solve a lot of our problems. And now I feel bad for telling the guy that he was theoretically correct but also crazy.
posted by olinerd at 2:29 PM on November 9, 2010

Uh, why? Most radio waves can't get through much water, so there wouldn't be much point in broadcasting underwater in the first place.

I admit, my knowledge of how submarines communicate with the outside world mostly comes from the movies Hunt for Red October and Up Periscope.
posted by nomisxid at 2:34 PM on November 9, 2010

http://en.wikipedia.org/wiki/Communication_with_submarines
posted by sebastienbailard at 2:46 PM on November 9, 2010

If you're not concerned about eye safety, ionizing oxygen in the atmosphere can make for an even more extreme antenna.

I want to combine that with a Van De Graaff generator and make a focused lightning gun.
posted by dibblda at 3:35 PM on November 9, 2010

Easy now, Nikola...
posted by wierdo at 4:48 PM on November 9, 2010

and make a focused lightning gun.

I once toyed with a similar idea as a way of act-of-godding someones house or tree with a lightning strike, and then I realized that my mind was doing that thing where it comes up with horrifically bad yet plausible solutions to evil intellectual exercises, so I used a combination of alcohol and blunt force trauma to forcibly remove the concept from my brain.
posted by quin at 5:07 PM on November 9, 2010