The Yagi-Uda project's programme dipole

dipole calculates the self impedance of a dipole. It is a very simple standalone program. You just give it the frequency, length and diameter of the dipole and it will give you the impedance in the form R + jX Ohms.

If you run it with no arguments, it will indicate how to use it.

sparrow /export/home/drkirkby/yagiuda-1.19/src % dipole
Usage: frequency(MHz) length(m) diamater(mm)

To find the self impedance of a dipole at 432MHz, that is 328 mm wide (0.328 m) and 8 mm in diameter we use:

sparrow /export/home/drkirkby/yagiuda-1.19/src % dipole 432 0.328 8
Self impedance of a dipole:
432.000000 MHz,  length 0.328000 m, diameter 8.000000 mm, is
Z = 62.043935  +8.655026 jX Ohms

If you want to use 4mm wire instead of 8mm, play around with the length a bit and you will soon see that making it 331.5mm long will give you about the same self-impedance.

sparrow /export/home/drkirkby/yagiuda-1.19/src % dipole 432 0.3315 4
Self impedance of a dipole:
432.000000 MHz,  length 0.331500 m, diameter 4.000000 mm, is 
Z = 63.928639  +8.762789 jX Ohms