Roy,

Thanks, I was able to enter the data into eznec and run the simulation. The
output was 'confusing'. Eznec predicted 100 Ohm over various grounds. Other
models predict 5 Ohms for the antenna plus ground resistance with a total of 10
Ohms or so. Which is correct? How can the differences be reconciled?

Thanks again - Dan

Roy Lewallen wrote:
dansawyeror wrote:

All,

I am creating a 'scaled' model of a loaded vertical. The model is
complete and in place. However I immediately realized I had no idea of
the 'theoretical' response. How can I calculate the expected impedance
response of a loaded vertical? It a mid load construction,

the base in #10 solid copper 4 inchs,
the coil is .6 pitch, 1 inch diameter, 5 turns #12, measuring .72 uH,
and the top is 4 inch #12.

The antenna appears to resonate at about 112 MHz.

The instrumentation, a directional coupler measuring reflection is
located at the base, directly under the 'ground plane'. This allows
measuring input and reflected signal strength.

The question is: How can I plot the expected impedance from say 100
MHz to 130 MHz?

Thanks - Dan


The free EZNEC demo from http://eznec.com will give you the information
you need.

Roy Lewallen, W7EL