The statement below about a 20 Percent tol on IP toroids is WRONG.? There is no such generic number.?
For type -6 material which is the most common material for HF use look at -
Note this is for a specific mafr but it appears generic toroids also "yellow - 6"? are made of Ni Cabonyl to the? MM specification.
The tolerance given is Plus minus 5 percent on AL.? that's for type -6 material for Type 18 my hardcopy manual says the tolerance is plus minus 10%
MM base their AL on a fully wound? toroid. and then back calc from there (measured uH at freq) to get the AL
If? you don't fully wind but also don't evenly space the windings around the core the effective AL will be less than tabulated.?
Timothy Fidler