4 ms·

Cool.. but can I make a home version of this for ham radio? I'm thinking of plastic tube from home depot + some kind of liquid metal and a pump.

Jtsummers 11y ago
http://www.wired.co.uk/news/archive/2010-11/09/sea-water-antenna http://www.wired.co.uk/news/archive/2010-11/09/sea-water-ant... Similar but using sea water.
zxexz 11y ago
You could probably do it with some sort of Gallium alloy, safer than mercury and more conductive. But I seem to remember them being more viscous? Maybe you could use some sort of Teflon coated radio-penetrable container and a peristaltic pump.
VLM 11y ago
If you allow moving parts may as well use a stepp-ir company antenna. For a blast from the past google "electrochemical hour meter" or try: http://globalepower.com/media/Coulometers-OBSOLETE.pdf http://globalepower.com/media/Coulometers-OBSOLETE.pdf So... say you have a tube of mercury and tiny electrolyte gap, then shove DC power thru it, and the mercury electroplates into one side. Takes thousands of hours per inch. That makes them great hour-meters for engines or whatever. Why, in only a year you could tune a dipole from one end of 20 meter band to the other LOL. I would imagine the end load capacitance might be a bit high, and the voltage limit being a bit low... But its an idea. They stopped selling those around the time they stopped selling things like mercury tilt switches, for some odd reason.
- deutronium 11y ago
  Heh, I was just about to post about mercury coulometers, I bought a number recently to play with (I had a silly idea of trying to make a watch with them) I connected one to 500V, and you could see lots of bubbles forming in the gap between the mercury. Krasnow has a nice video of them https://www.youtube.com/watch?v=Cxj399LuX1M https://www.youtube.com/watch?v=Cxj399LuX1M showing a view of them through a microscope
  - morcheeba 11y ago
    Aw, that's an awesome idea! Why didn't it work? Some quick math... To get the bubble to go across a 2400 hour meter in 24 hours, you'd have to run at 100x12v = 1200 volts. I guess it wasn't stable at 500v? Also, no idea how the current/voltage scales, but normally this is .72mW ... at 100x it's still 72mW -- not too bad.
    - deutronium 11y ago
      It may still work, but I managed to break the coulometer with some mercury leaking out, when trying to prise open the casing, to get a better view under my microscope. I'm going to try again with another one soon :) One thing I'm worrying about though, is if the higher voltage causes the mercury to get to a temperature that leads to the glass breaking under heat.

Jtsummers 11y ago

http://www.wired.co.uk/news/archive/2010-11/09/sea-water-antenna http://www.wired.co.uk/news/archive/2010-11/09/sea-water-ant... Similar but using sea water.

zxexz 11y ago

You could probably do it with some sort of Gallium alloy, safer than mercury and more conductive. But I seem to remember them being more viscous? Maybe you could use some sort of Teflon coated radio-penetrable container and a peristaltic pump.

VLM 11y ago

If you allow moving parts may as well use a stepp-ir company antenna. For a blast from the past google "electrochemical hour meter" or try: http://globalepower.com/media/Coulometers-OBSOLETE.pdf http://globalepower.com/media/Coulometers-OBSOLETE.pdf So... say you have a tube of mercury and tiny electrolyte gap, then shove DC power thru it, and the mercury electroplates into one side. Takes thousands of hours per inch. That makes them great hour-meters for engines or whatever. Why, in only a year you could tune a dipole from one end of 20 meter band to the other LOL. I would imagine the end load capacitance might be a bit high, and the voltage limit being a bit low... But its an idea. They stopped selling those around the time they stopped selling things like mercury tilt switches, for some odd reason.

deutronium 11y ago
Heh, I was just about to post about mercury coulometers, I bought a number recently to play with (I had a silly idea of trying to make a watch with them) I connected one to 500V, and you could see lots of bubbles forming in the gap between the mercury. Krasnow has a nice video of them https://www.youtube.com/watch?v=Cxj399LuX1M https://www.youtube.com/watch?v=Cxj399LuX1M showing a view of them through a microscope
- morcheeba 11y ago
  Aw, that's an awesome idea! Why didn't it work? Some quick math... To get the bubble to go across a 2400 hour meter in 24 hours, you'd have to run at 100x12v = 1200 volts. I guess it wasn't stable at 500v? Also, no idea how the current/voltage scales, but normally this is .72mW ... at 100x it's still 72mW -- not too bad.
  - deutronium 11y ago
    It may still work, but I managed to break the coulometer with some mercury leaking out, when trying to prise open the casing, to get a better view under my microscope. I'm going to try again with another one soon :) One thing I'm worrying about though, is if the higher voltage causes the mercury to get to a temperature that leads to the glass breaking under heat.