"gareth" wrote in message ...

"Wayne" wrote in message
...
"gareth" wrote in message ... "Wayne"
wrote in message
...
Well, I don't know what you are calling "retarded potential".
It is the term for the electric potential that must have existed on an
antenna when
analysing the radiated signal at some distant point.
It is termed, "retarded" because the radiation originated at some time in
the past.
OK now I know. I hadn't heard the term before.
But, how about my question?
" if the radiated power is equal for two different antennas, why would
the field strength be different, except as related to pattern
differences?"
The radiated power just is spread out differently.

Quoting from Electromagnetism by F.N.H.Robinson in the Oxfors Physic
Series,
1973 edition ISBN 0 19 851806 4, Chapter 11, Radiation and page 100 ..

The radiated power is proportional to the current times the antenna length
divided
by the wavelenght, and all squared.

Therefore, to achieve the same radiated power from a short antenna, the
current
in the antenna has to be higher.

But wasn't it implicit in your original statement that the power was equal
in both the 1/4 wave and the shorter antenna?

So for your assertion, we don't need to know the current.