Which ferrite material works well for the AM band around 1 MHz?


Here's what seems like a hi-Q a crystal set using toroids:
http://www.crystalradio.net/contest/paul.html

It uses "two toroid cores, Palomar Engineering T-130, broadcast band
frequency material". Unfortunately it doesn't say the kind of core, but from
the number of turns and the capacitance I figured that it must be type 26
(yellow/white). I think this is a rather uncommon kind of material, it has
one of the highest mu's, 75, compared to mu=10 for type 2 and mu=8 for type
6. Anybody with experience with this kind of material?

Sverre
LA3ZA