[TowerTalk] antenna impedence and ground impedence??

[Tom Rauch]

> I have a questions regarding calculating ground impedance. How can this
> be measured??

I think you are asking about ground resistance, rather than impedance.
Measuring ground resistance can be very difficult unless you know every
other variable involved, including everything about the effects of
surroundings.

> The impedance of a loaded vertical measures about 50 ohms, however model
> programs predict the antenna impedance is in the range of 10 ohms. Does
> this imply ground impedance is 40 Ohms??

No. But it does indicate you have something seriously wrong with the
antenna, the model, or a combination of both.

I assume you have a loading coil. It is not possible for most people to
measure loss resistance in a loading coil, so you don't know that value.
Even if you knew the loading coil ESR, you would have to normalize the loss
resistance of the coil to the feedpoint of the antenna since that is the
reference point of the measurement.

It is also very difficult to measure actual radiation resistance.

Radiation resistance, at least by any meaningful use of the term, is NOT
the real part of the feedpoint impedance. Ground loss resistance is not the
difference between the radiation resistance and feedpoint resistance except
under very specific conditions.

What is the antenna?

73 Tom