Brian wrote:
.... 43 is the best for 2-30 MHz right?


Depends on you application. Are you using the toroid for noise
suppression, or as a broadband transformer, or for winding inductors?
According to the Fair-rite website, for noise suppression applications,
Type 43 is better for 20-100 MHz .

The www.Fair-rite.com website has several technical articles
(application notes) that you may find helpful.

73,

Duane, N6JPO