In article ,
"Al" wrote:

wrote in message
oups.com...
Telemon I was going to Email this info but your addy is bogus. I
wanted to inform you of my test results and to give you the few
additional refferences I located. I will be greatly shocked if I
ever post again. Too much risk and way too little reward. Terry


Terry and Telamon, Your posts and links are very informative and I
appreciate you guys posting this type of information.

Telamon your previous comments on impedance and reactance is also
very much appreciated. I'm still confused on why impedance is not
frequency dependent, but I'm working on it.

Snip

An antenna or transmission path has a characteristic impedance based on
its physical characteristics. This is a property different from
reactance, which is a response to some frequency. Example would be a
folded dipole compared to a dipole. The characteristic impedance of the
dipole is about 72 ohms but the folded dipole is four times this at 288
ohms due to a division of current paths in that design. This is an
effect also seen in transformers where the impedance ratio value is the
turns ratio squared.

A single wire Marconi type can be thought of as a transmission line
where the two conductors are the wire and the earth under it as the
other conductor. Based on this the RF current in the wire will see a
characteristic impedance as determined by the wire diameter and the
distance from ground with air as the dielectric between them.

Larger diameter wire for the same distance will cause the wire to
assume a lower impedance and the closer the wire is to the ground the
impedance would also be lower.

Whatever the characteristic impedance of the wire is if you stimulate
it with energy at some frequency it will react to that energy with a
combination of the characteristic impedance and added to that a value of
impedance based on the electrical length of the wire. The reactance of
the the wire would be the combination of the characteristic impedance
and the reflected energy together.

The consequence of the aforementioned situation is the reactance of the
wire will swing from very small values to very large values through the
characteristic impedance value of the wire and basically you will also
get this same response from classical Hertizan antenna types. The
characteristic impedance of the wire will be measured with a zero
reactance value.

When you stimulate an antenna at a resonance point then the energy you
put into it is not being bucked by a reflected wave of energy coming
back at it at some phase combination of forward and backward energy and
so the antenna looks like a resistive load where this resistance is a
combination of the conductor losses in the antenna elements and the
radiation resistance of the antenna.

The characteristic impedance is measured when the antenna appears to be
a resistive load with no reactance added or subtracted from that value
is another way to look at it. Another way of saying this is all the
energy goes into the antenna, which appears to be just a resistor of
some value.

I wrote this a couple of different ways, being redundant of purpose.
Does this make sense to you now?

--
Telamon
Ventura, California