On Saturday, June 2, 2007 at 1:54:28 AM UTC+10, wrote:
I came across two ferrite toroids with the measurements of 35mm
diameter, the hole in the middle is 21mm and it is 13mm thick. On the
packet it says that the ferrite material is L15. Does anybody know if
L15 is equivalent to 43 or 61 ferrite material? I have searched the
net but have been unable to find any information. Any information
would be appreciated. Cheers.

Owen was was right saying 259 can't measure inductors with impedance over j500, say j4788. With small VNA you get accurate scan over entire HF.
Roy seems to be using 259 for everything, including making pizzas.
I know only one way for 259 to be accurate with high impedance inductor. Add capacitor and 50 ohms in series with inductor, and 259 becomes very accurate around resonant frequency. I doubt there is another way to do it properly.
Tino VK3EGN