capacity hat antennas
 

wrote:
(snip)
I suggest you read:

http://www.w8ji.com/radiation_and_fields.htm
(snip)

I am trying to soak up the information on this page.

In the graph of field impedance versus distance (about half way down
the page, is this showing the ratio of E field to H field intensities
I would measure with very small electric and magnetic pickups placed
at these distances?

It looks like this is showing that a mag loop creates a larger E field
at some distances than a dipole that is creating the same far field
energy propagation. This is quite counter intuitive, so I want to
make sure I have not got it wrong.

Capture Area (was antenna theory for idiots?)
 

John Popelish wrote:
Is "height" in "effective height" really referring to effective
radiating length, rather than something to do with elevation above
ground (assuming that one is talking about a monopole above a ground
plane)?

In other words, is the "effective height" of a horizontal dipole
actually related to its end to end length, not its distance above ground?

I am just trying to get started on the right foot in my reading.

Never mind. I found something you wrote in an earlier thread:

"There's a common term for the relationship between
the field strength and the length of a conductor,
called the "effective height" or "effective length".
The voltage at the center of a dipole in a field of
E volts/m is simply E * the effective length.
The concept is valid for any length conductor,
not just short ones. The effective length of a
uniform-current dipole is equal to the wire length.
The effective length of a short conventional dipole is
0.5 times the wire length. The effective length
for receiving is the same as the effective length for
transmitting -- in transmitting, it relates the strength
of the field produced to the *voltage* -- not power --
applied across the feedpoint.

If you apply 0.5 volts to a standard dipole
and 1.0 volts to a uniform-current dipole,
the power applied to each will be the same
because of the 1:4 ratio of radiation resistance,
and the generated fields will be the same.
This is consistent with the antenna gains being the same."

This cleared up a lot of the terminology and concepts for me.

Capture Area (was antenna theory for idiots?)
 

"Effective length" refers to dipole type antennas in free space.
"Effective height" is the equivalent property of a grounded monopole.
They're often used somewhat interchangeably.

Roy Lewallen, W7EL

John Popelish wrote:
Is "height" in "effective height" really referring to effective
radiating length, rather than something to do with elevation above
ground (assuming that one is talking about a monopole above a ground
plane)?

In other words, is the "effective height" of a horizontal dipole
actually related to its end to end length, not its distance above ground?

I am just trying to get started on the right foot in my reading.