"John" napisa³ w wiadomo¶ci
. au...
Whilst trying to source a "digital" TV antenna I came across some with all
external surfaces plastic. One was a small yagi with all external surfaces
plastic, hopefully with metal elements embedded. Another a "T" shape made
out of plastic conduit with elements inside conduit.
My question is how do they work?. If they are detecting electrical fields
how does increasing source impedance by 100,s of megohms improve things?.
Capacitive coupling, I suppose at the frequencies involved there would be
some.

Yes. The frequency do the work.

Rob wrote: "Apparently you have missed the interesting discussions with our
Polish
friend."

It was not the discussion. I only citate the Giants:
"In 1867 Lorenz wrote: " Ludvig Valentin Lorenz, "On the identity of the
vibrations of light with
electrical currents," Philosophical Magazine, Vol. 34, 1867, p. 287-301"

http://books.google.pl/books?id=caJd...page&q&f=false

On p. 301 he wrote:
"The present general opinion regards light as consisting of backward and
forward motions of particles of aether."
If this were the case the electrical current would be the progressive motion
of the aether in the direction of the electrical current."

In today's words: "Light is the oscillatory flow of electrons".

So no problem for electrons to flow through the plastic if it is matched to
the frequencies.
For example,You must use the different type of glass for different wave
length.

The ice is O.K. for the RF but the water not.

If it works as well as all metal why doesn,t every one use it and stop
corrosion?
Hope this is not too off topic.

It is too off the teaching programs.
S*