Re: NEC-LIST: GPR antennas

Dear Max,

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

      Respectfully, Joe Jahoda

"Max J. Schmitt" wrote:

> Pascale :
>
> I would suggest to use a ferrite-loaded dipole. For example, use
> low-loss Nickel-Zinc (Ni-Zn) ferrite bars, 10 - 20 mm thick, embedded
> in an Aluminum channel of dipole length. The Ni-Zn ferrite should have
> a permeability of between 100 and 50 over the frequency range of 5-50
> MHz.
>
> My estimate is that you could reduce the dipole length by a ratio of
> 3-5, i.e., at 8 MHz from 12.5 m to 2.5 to 3.5 m.
>
> There are Ni-Zn ferrites with fairly high permeability up to
> approximately 100 MHz. Depending on the average power to the antenna,
> you want a low loss tangent.
>
> Bonne Chance !
>
> Max J. Schmitt
> Cons.Eng.
Received on Tue Apr 04 2000 - 03:59:32 EDT