Half a croissant, on a plate, with a sign in front of it saying '50c'
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Fluid filled adjustable antenna

Physical length of antenna adjusted by adding and removing conductive liquid
  (+7, -3)
(+7, -3)
  [vote for,

Could a multi-frequency amateur radio(or other type)antenna be created, with an easily variable mechanical length, by filling a tube with conductive salt water, possibly ferromagnetic fluid, or metal particles and oil, for example, and changing the mechanical length of the antenna as needed by pumping liquid in and out of the tube? The antenna would be sensitive to movement and would have to be stationary

Edit 2010 9 17: Edit 2010 9 17 - Thank you for the anti-freeze requirement observation. I recently considered this fluid filled antenna a limited RF antenna space/complaining neighbors/ "no antennas allowed/" neighborhood covenant alternative. The following comments came from my reply to a blog referencing a new house wiring antenna design to control household wireless gadgets. Further refinements include a T connector (preferably see-through) if a dipole or other multi-armed antenna is created (a vertical is the best implementation, a multi-arm antenna would require horizontal installation with a slight upward tilt, at least until anti-gravity mechanisms are developed; an antenna tuner, a 50 ohm connector to the radio, a ground, a conductive fluid that will not freeze, and a compatible fluid pump and controller with variable electrical or mechanical detents set for pre-defined radio bands (even specific frequencies once tuned if the conductive material did not evaporate or leak). The opaque liquid will drain to create a hard-to-see antenna when not in use (the tubing material could not retain a stain), or become a perpetual hard-to-see antenna if a clear liquid is used. A two piece "tube in a tube" requires less potentially weighty conducting fluid, and will force the fluid to the outer surface/wall where the RF is actually emitted.

Sunstone, May 27 2008

Liquid Metal Antennas http://www.eham.net/articles/13251
Uncovered when researching the equally baked "flowing metal heatsink". [phoenix, May 27 2008]

Liquid Metal Antenna http://www.hamdomain.com/lm-antenna/
The designer's page. [phoenix, May 27 2008]

Variable frequency seawater fountain antenna http://www.youtube....watch?v=9tIZUhu21sQ
Variable frequency seawater fountain antenna [Sunstone, Aug 29 2010]

Fluid filled, and adjustable http://www.dfg.ca.g...-lobster-hi-res.jpg
...and tasty. [normzone, Sep 01 2010]

Tuning into Nature book http://www.thefreel...insects-a0163395921
Book and concept article [Sunstone, Sep 18 2010]

House wiring antenna http://www.kurzweil...w-power-sensor-data
House wiring acts as electromagnetic frequency antenna, posted as reference to 2010 9 17 edit [Sunstone, Sep 18 2010]

America’s navy is developing a [tube encased] antenna made of seawater https://www.economi...d=18007506&fsrc=rss
Update on Naval Fluid filled adjustable antenna, from water spout to contained in a tube, just like this one [Sunstone, Jan 30 2011]


       Possible, but nearly as effective to use a log-periodic antenna ....
8th of 7, May 27 2008

       Alternatively, pumping conductive liquid in or out of a hollow tube could change its electrical length without affecting its mechanical length at all. Somehow this seems a lot more elegant to me.
Wrongfellow, Sep 01 2010

       Yes, but this fixed mechanical length approach would not have the organic spectacle of the rock and roll getting louder and clearer as the antenna stretched longer and longer, shuddering and twitching as it rises up from the ground.
bungston, Sep 01 2010

       //Alternatively, pumping conductive liquid in or out of a hollow tube could change its electrical length without affecting its mechanical length at all.//   

       Uh, I think that's exactly what the poster was saying....
MaxwellBuchanan, Sep 05 2010

       I dunno. I got the impression he was talking about an antenna //with an easily variable mechanical length//, //changing the mechanical length of the antenna as needed//.
Wrongfellow, Sep 06 2010

       Depends how you phraze it......
8th of 7, Sep 06 2010

       Just out of curiosity...   

       Would frozen conductive liquid work as an antenna too?
DrWorm, Sep 07 2010

       Any conductive material will work.   

       (Does metal count as a "frozen conductive liquid"?)
Wrongfellow, Sep 07 2010

       So, a salty popsicle could he used as an antenna?
DrWorm, Sep 07 2010

       Reply to normzone's fluid filled and adjustable link regarding a lobster: See Phillip S. Callahan's fascinating "Tuning into Nature" book.
Sunstone, Sep 18 2010


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