From: "Dr. Barry L. Ornitz" <ornitz@usa.net>
Newsgroups: rec.radio.amateur.homebrew
Subject: Re: Raising coil Q in regen RX- Glass Properties
Date: Thu, 8 Feb 2001 01:10:26 -0500

"Filippone" <filippone@my-deja.com> wrote in message
news:95si3o$9r3$1@nnrp1.deja.com...
> Ian, I used to share this belief, but I now have my
> doubts.  A microwave oven works at one well defined
> frequency.  Isn't that a f. that is easily absorbed by
> water?

I am not sure how many times this needs to be said...

Microwave ovens operate at different frequencies in
different countries.

Microwave ovens do not operate at any resonant frequency of
water molecules.

Water is a broadband absorber (lossy dielectric) at an
extremely broad range of frequencies.

> And, isn't deionized water also a pretty decent electrical
> insulator?  (I even saw it used in hydraulic remote
> control of high voltage switches!).  Yet, pure water does
> heat a lot in a microwave....

The heating has nothing to do with actual elecrical
conduction.  What you are seeing is hindered rotation of the
water molecule as its dipole tries to align with the applied
electric field.  The rotation requires energy and it is this
energy converted into heat.

Adding a small amount salt to distilled water causes a huge
increase in its DC conductivity, but it only increases the
microwave losses slightly.

        73,  Barry     WA4VZQ     ornitz@usa.net