LF: Re: Ferrite Loops

["James Moritz" <james.moritz@btopenworld.com>]

Dear Tom, LF Group,

> what do you think about an array of many parallel mounted ferrite rods, 
> each of them carrying only a few windigs, all windings connected in series 
> (and then perhaps tuned) and the rods arraged in such a way that the 
> individual apertures dont touch? Or will this lead to the dimensions of a 
> comparable air loop ;-) ?
I am sure this would work, but I think you have also identified the 
limitation ;-) Fundamentally, if the signal has a particular power density 
at the receive site, the antenna must intercept the signal from a certain 
aperture area in order to deliver a certain power to the receiver. So there 
is a limit to how small it can practically be, although the actual shape can 
vary to obtain the same aperture - one could make a rough comparison between 
the short, wide loop vs. the long, thin ferrite rod, and a long yagi vs. a 
broadside array of dipoles.
I think an array of ferrite rods might be attractive in some circumstances - 
for instance, you could have numerous small rods stacked vertically, to 
produce a "ferrite rod vertical" with a small turning circle but a 
relatively large effective area.
Cheers, Jim Moritz
73 de M0BMU