rickman wrote:
On 10/4/2015 10:05 AM, John S wrote:
How less efficient is a short vertical than a 1/4 vertical?

You are starting to sound like someone else.


I would like to see some numbers. It is a ground plane with 4 radials
(typical). Free space.

Assume a source at the base. The type of source is your choice. EZNEC
defaults to one amp, but can be changed to a constant power of your choice.

I'm sure I've left out additional requirements, but maybe this will be a
healthy discussion even so. Suggestions are welcome.

Don't you need to define all the characteristics of the antenna? I
guess an impedance specification will suffice.

It doesn't work that way.

You define the physical structure, including the material size and
type as well as the environment and EZNEC calculates the impedance,
material loss, voltages, currents, near and far fields.

I don't know what electrical model EZNEC uses for the transmitter, but
won't you need to deal with impedance mismatch at that point? Or does
the model use a current drive with infinite impedance (or conversely a
voltage drive with zero impedance)?

Like all circuit analysis programs, EZNEC uses ideal sources; you select
the type.

The default reference impedance is 50 Ohms, but can be set to anything.

Is the material some real material or lossless?

What you will find is that the only loss in the ANTENNA in free space
is the I^2R loss of the material.



--
Jim Pennino