Re: NEC-LIST: Efficiency of Short Dipoles

Andre Fourie wrote:
>
> I just noticed your reference to mu(r) of stainless steel rope as a
> potential source of additional loss in HF antennas, presumably
> because:
>
> skindepth = 1/sqrt(mu * sigma * constant)
>
> and hence losses increase proportional to sqrt(mu(r)).
>
> My information indicates that mu(r)= 1 at HF frequencies for most
> steels, irons and other non-laminated metals.(gyromagnetic limiting
> frequency approx 20 kHz).

I looked into this some years ago and the magnetics textbooks (I recall
Bozorth in particular) seemed to me to be saying that ferromagnetic
behaviour endured up to a few hundred MHz at least.

Peter Excell
Received on Wed Dec 17 1997 - 12:52:13 EST