Do you have your ground planes separated from the radiator in the model?

Do you have the source placed at the bottom end of the radiator?

Perhaps one more versed in EZNEC would take a look if you would
post/offer the antenna file you have created here...

John

"redhat" wrote in message
ups.com...
i have made a modification to it, it is now 1/4 wavelength monopole.
the simulation output is : source voltage= 3092 at -89.79 deg. and
impedance= 11.08-j3092 ohm . what is the meaning of this source
voltage? i have placed a source with amplitude 1v at 0% from E1
because
it is a monopole, the ground type is free space.