Short dipole antenna impedance model (Python code)

from math import log
from numpy import pi, tan
from numpy.polynomial.polynomial import polyval


# Short dipole antenna impedance model

f = 27e6             # frequency
La = 1.4             # total dipole length
Dia = 0.001          # diameter of the conductor

wavelen = 3e8/f
k = 2*pi/wavelen     # wave number
z = k*La/2;
R = polyval(z, [-0.4787, 7.3246, 0.3963, 15.6131])
X = polyval(z, [-0.4456, 17.00826, -8.6793, 9.6031])
IM = 120*(log(La/Dia)-1.0) * 1.0/tan(z) - X

print  'Real:', R, ' Imag:', IM