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From: David Jefferies
Date: 23 Mar 2002
Time: 14:13:03
Remote Name: 195.92.194.18
Bill,
I'd have thought it would have had some effect. But the students' initial results seem to tell us that even 3cm thickness of epsilon = 5 dielectric on a 15 cm long dipole doesn't make a clear measurable effect.
However, J R James produced a compact antenna loaded with high epsilon ceramic which was significantly shorter, for a thickness only about equal to the metal rod diameter.
Mind you, as with statements of proponents of compact antennas generally, I am very loth to accept reported experimental measurements without a great deal of caution and convincing. (Except from a very few students who I know to be sound.)
What I think is that for most thin rod antennas, the electric stored energy is minimal close to the antenna and therefore I wouldn't expect the dielectric to have much effect. J R James showed me a ferrite loaded antenna which works better than the dielectric loaded one, except that it is lossy.
It is very unwise to speculate in the absence of sound measurements, as far as antenna properties are concerned.
DJJ