Re: NEC-LIST: GPR antennas

joe jahoda wrote:
>
> Dear Max,
> We at Astron have tried various versions of what you ahve suggested,
> but unfortunatly have never achieved the desired forshortening, plus the
> bandwidth deteriorated. After nuch effort we realized the technical
> problems. If anyone has achieved the desired square root of the
> permeability I would love to hear about it?

Dear Joe,
 
My suggested length reduction with ferrites was only 30-50 percent of
the resulting square root of mu ! I have experimented mostly with
ceramic dielectrics for size reduction and much less with ferrites.
 
I had achieved significant reductions by loading slot antennas. My
research has shown that the degree of length reduction depends on :
 
1. permittivity or permeability of the dielectric or ferrite
2. thickness of the loading material
3. type of antenna
4. effective dielectric constant or permeability
 
Of course for transmit antennas you need a low loss factor. Only
expensive computer programs can model diel./ferrite loaded antennas.
 
Max Schmitt
Cons.Eng.
Received on Tue Apr 04 2000 - 04:04:07 EDT