Richard Harrison wrote:
1/2 or more of the power received by a receiving antenna is re-radiated.

Nearly all of the power received by a transmitting antenna is
transmitted.

Expanding a bit to make the receiving and transmitting systems symmetrical
with respect to power: If the transmitter is linear (like the antenna
is linear), i.e. Class-A, 1/2 or more of the generated power will be lost
in the source. In a linear resonant system, about 1/2 of the power sourced
reaches the antenna and about 1/2 of the received power makes it to the
receiver. It's the old maximum power transfer theorem at work.

A receiving antenna must be resonant to enable full acceptance of
available energy, and it must be matched to avoid re-radiation of more
than 50% of the energy it is able to grab.
If off-resonance, the receiving antenna has too-high impedance for
significant induced current. Of course, we have such good receivers we
can do without good efficiency.

A properly tuned antenna tuner ensures that the *antenna system* is resonant
for both transmit and receive (assuming the receiver's input impedance is the
same as the transmitter's output impedance). Note that an off-resonant antenna
*wire* is integrated into a resonant antenna *system* through the use of an
antenna tuner. Chapter 7 in _Reflections_II_ explains how even though it might
better have been titled, "My Transmatch Really Does Tune My Antenna" *SYSTEM*.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----