Fluid filled adjustable antenna

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.