In message , Dave Platt
writes
In article ,
Ian Jackson wrote:

Are there any calculations or charts for centre impedance of a dipole in
free space, starting from zero length, and going out to infinity?

I think that what you're looking for is in Kraus "Antennas for All
Applications", page 446 - "Self-impedance of a thin linear antenna".
The formula given is based on the induced-EMF method... it's an
approximation which apparently works well for cylindrical antennas
whose length is at least 100x the diameter.

Thanks for that. I've found a free download of a PDF copy (18MB) at:
http://www.badongo.com/file/9893801
I'll have a look to see if it is what I want.

I would have thought that the feed impedance of a dipole at a wide range
of frequencies/lengths (ie 'very short' to 'very long') would have been
fairly typical rule-of-thumb required information for those interested
in antennas. However, it does not seem to be!
--
Ian