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John_BS · 11th Jun 2021, 10:10 am

If you're sure the new coils resonate at 1.4MHz, they must be less than 5uH. It seems strange that the one with a core resonates at the same frequency as I'd expect that to show at least 1.5 times the inductance with the same number of turns? Can you check the turns you have on both.

So, assuming the 1.4MHz figure is correct, that implies your new inductors are around 4uH, so you need to add turns, not remove them. You're aiming for around 7.5 to 8uH, so the number of turns should be increased by a factor of around 1.4
John

PS if you can post the details of those ceramic coils (diameter of actual coil, length of winding, no of turns), we can work out the inductance pretty accurately.

11th Jun 2021, 10:10 am	#7
John_BS Octode Join Date: Dec 2008 Location: Wincanton, Somerset, UK. Posts: 1,782	Re: Modifying an inductor? If you're sure the new coils resonate at 1.4MHz, they must be less than 5uH. It seems strange that the one with a core resonates at the same frequency as I'd expect that to show at least 1.5 times the inductance with the same number of turns? Can you check the turns you have on both. So, assuming the 1.4MHz figure is correct, that implies your new inductors are around 4uH, so you need to add turns, not remove them. You're aiming for around 7.5 to 8uH, so the number of turns should be increased by a factor of around 1.4 John PS if you can post the details of those ceramic coils (diameter of actual coil, length of winding, no of turns), we can work out the inductance pretty accurately.