On Sun, 18 Dec 2005 07:03:23 GMT, "Asimov"
wrote:

"Roy Lewallen" bravely wrote to "All" (17 Dec 05 12:44:06)
--- on the heady topic of " Underwater"

RL From: Roy Lewallen
RL Xref: core-easynews rec.radio.amateur.antenna:221425

RL The attenuation of a radio signal through water is staggeringly high
RL except at extremely low frequencies. Fresh water is lossy for two
RL reasons: one is that the polar molecules attempt to align themselves
RL with the oscillating electric field. This physical motion results in
RL loss.
[,,,]

Thanks for the info. I had read that submarines communicated in a
band of a few 10's of Hz because of the problems with water.

The BW is a product of the information bit rate and the fundamental
frequency. Water enters the picture to drive the fundamental
frequency.

As for the polar molecules aligning themselves, this implies it takes some
time to achieve.

Displacement time by ionic polarization can be as short as s/10¹³

Thus there is a resonnant point in this and if there
is resonnance then there might be anti-resonnance too. Might you know
where this natural molecular resonnance is? Might this be the standard
microwave oven frequency?

For water? salt water? at what temperature? Ice, whose relaxation
time can vary one order of magnitude for each 10°C, is considerably
different from water. Its conductivity plunges like a rock with
temperature too (at roughly the same rate) to become a nearly perfect
dielectric.

The relaxation time for Ice runs in the kilohertz whereas for water it
is in the high gigahertz (and has nothing to do with the microwave
oven frequency as simple heating shifts this relaxation time one order
of magnitude between freezing and boiling). Yes, 6 orders of
magnitude change when going from 0° ice to 0° water.

Attenuation figures may follow this post.

73's
Richard Clark, KB7QHC