[TowerTalk] 160m vertical and the number of radials

[Dan Maguire]

K6STI wrote:
>>> I'll use this as an excuse to plug my ground probe calculator. Build your own ground probe and use my calculator to go from the probe impedance, as read with a VNA, to ground permittivity and conductivity.

>>> The calculator is free and worth every penny:

>>> http://ham-radio.com/k6sti/gnd.htm

Marginally related.  In the README.TXT for Brian's Ground Probe
Calculator 3.20 you'll find this statement:

"Wavelength in soil is much shorter than in air."

With EZNEC, including the now free v. 7.0 (https://eznec.com/), from
the main window you can click on Utilities > Ground Info to see a
detailed list of the ground characteristics for the current
combination of Frequency and Ground Description.  In the following
image the first three examples are for "Average" ground (conductivity
0.005 S/m, relative permittivity [dielectric constant] = 13) at 1.8,
7.0, and 28.0 MHz.  Notice how both the velocity factor and skin depth
vary with frequency.  The "Wavelength in soil" is of course Free Space
wavelength * VF.  The second three examples are for different Ground
Descriptions all at 1.8 MHz.  Again note the significant change in
both velocity factor and skin depth.

https://i.postimg.cc/Kjx789DT/image.png

The K6STI program output shows permittivity and conductivity in mS/m
along with frequency in MHz.  You can correlate that with EZNEC by a)
making sure the EZNEC Ground Type is Real / High Accuracy or Real /
Extended Accuracy, b) clicking on Ground Descrip and then entering
custom values for Conductivity and Dielectric Constant, noting the
swap in the order of the parameters and the change in units for
conductivity, and c) setting the Frequency.  If the Frequency field
shows as "(Sweep On)" click Setups > Frequency Sweep and change On to
Off.

Here's an example using the sample data from the K6STI gnd.zip file
(http://ham-radio.com/k6sti/gnd.zip) and with metric units.

https://i.postimg.cc/Kv97mDkK/image.png

Dan, AC6LA