High Al (high permeability) ferrites are very useful at RF. They're
widely used for broadband transformers, baluns, and EMI suppression
chokes, and are in fact very often the best choice for those
applications. If DC current is low enough to avoid saturation, they also
make excellent RF chokes -- ones that maintain a high impedance over a
very wide bandwidth and don't show any appreciable self resonant effect.

The only RF application they're not good for is inductors in tuned or
high-Q circuits, such as filters and tank circuits, or as tuned
transformers.

Roy Lewallen, W7EL

mike wrote:
On Fri, 19 Sep 2003 12:31:56 -0700, Cecil Moore
wrote:




I was looking for a cheap source of toroids and stumbled across a
blown ATX computer power supply. It was chock full of toroids.



Probably powdered iron cores and not very useful at RF frequencies.


Yep your right. I found them to be mostly very high Al....totaly
useless at RF frequencies.

mike