wrote in message ...
On Sat, 08 Jul 2006 16:08:23 GMT, John - KD5YI
wrote:

Actually, when properly matched, it radiates half the received power.

True, but it's such a low level as to normally be considered
insignificant. Unfortunately some take that to mean there is none.

If there were none, a Yagi antenna which used all passive elements
save for the driven element would not work. On receive that driven
element plays an active (pardon the pun) roll.


Still, that's a special case.

I can choose a different special case with a different result.
For a large, high-gain aperture-type antenna such as a big horn or dish,
virtually the received energy orthogonally incident on its cross-section
will be sucked up and absorbed.

Therefore you can't really say that an antenna always radiates at least
half the received power.

Don