Small Short HF RF Antenna

[rrecroc]

Greetings To All,

I need some help. I am in the process of doing some experimentation that involves exposing various liquids to a wide spectrum of RF energy. This will involve direct submersion of “antenna” into the liquids themselves.
Because of the limited volume of the liquids I will be using, the antennae will have to be short ...... sub-multiples of the various wavelengths (actually I will be working with volumes that can be held in standard lab beakers).
Does anyone know of anyone who sells such antennae.
Or perhaps I could make my own ........ what materials should I use and how do I measure and cut them accurately?
Any ideas would be greatly appreciated.

Thanks,

Rick

[m0bov]

Comet do various telescopic antennas for HF, they are going to be up to a meter or two long. You may hit one problem, most HF (if not all) use a loading coil to tune the whip, so most antennas for portable sets are the same physical length, the coil does'nt radiate just in case this causes problems. What sort of liquids are you using? Surley since the liquids conduct, the antenna won't tune up?

[5B4AJB]

There was a discussion about this on the Yahoo 5B4 forum recently.

All (most of) the energy is "grounded" by the water.

Propagation is therefore limited to ground-wave.

Lower frequencies (Hz-kHz) seem to suffer less (submarine radio).

There is commercial diving kit available, but it seems to use 2/4 wires
http://www.subtechsystems.com/diverradios.htm

Maybe it would be more efficient to run coax to the surface with the antenna on a float.
On the other hand A.F. seems to propagate better through water than it does through air...

[rrecroc]

The liquids are poor conductors ........ that is not to say there will not be some current flow and there is also the current flow from capacitive effect at higher frequencies ....... the tests in the first phase will begin at 1 Mhz and may go as high as 100 Mhz.

[m0bov]

Hi, I very much doubt you'll get much from a short antenna at 1Mhz, it will need a massive loading coil!

[rrecroc]

Not so sure the "grounding" effect is negative as the purpose of the experiment is to measure the effects on the liquid ....... propagation beyond the liquid is not a concern .....