On Fri, 21 Nov 2003 06:57:23 +0100, "Meindert Sprang"
wrote:

"Gary Schafer" wrote in message
.. .
Easiest way to visualize it is with open wire line which has very low
loss. Feeding a non resonant antenna the SWR can be very high on the
line. You can have 50% reflected power on the line. With 100 watts
forward you would then have 50 watts reflected but just about all of
the 100 watts will reach the antenna and be radiated. The only loss
will be the very small loss in the line. (typically a few tenths of a
db loss)

But if all energy is radiated by the antenna, how on earth can you have any
reflected power???? I thought the essential part here is that reflected
energy is the energy that os NOT radiated.

Meindert


Think of it this way: You have the same mismatch to the feed line on
both ends.

If your antenna provides a 70 ohm load for a 50 ohm feed line you will
have reflected power from the antenna. That mismatch of impedance is
reflected back down to the transmitter end of the line. The feed line
at the transmitter NO LONGER LOOKS LIKE A 50 OHM LOAD. If a matching
device is placed between the transmitter and the feed line it must
provide the same match at the transmitter end as the antenna does at
the other end of the line. Called a conjugate match. (you can read
about it in your handbook) It is usually a complex impedance made up
of resistance and capacitance or inductance.

Having the same mismatch on each end of the feed line will provide the
same amount of reflected power at both ends of the line. So any power
that gets reflected from the antenna because of the mismatch there
will get re-reflected back toward the antenna again because of the
similar mismatch to the line at the transmitter end.

Regards
Gary