If you can it is always worth measuring the inductance of a toroid core rather than relying on the various charts and on line calculators that tell you how many turns equate to an particular inductance.
I was making an LPF for 20 meters the other day and discovered that the chart I was using told me I needed 17 turns for a particular inductance, however when I measured the inductance I only needed 15 turns. With the extra turns the LPF would not have performed as required....
73s Steve G0XAR
