[Elecraft] OT: J and -31 mix toroids
David Cutter
d.cutter at ntlworld.com
Mon Apr 6 19:31:03 EDT 2009
Subject: Re: [Elecraft] OT: J and -31 mix toroids
> You might wish to experiment with Steward mix 35 or 40 toroids. Mix 35
> has a relative permeability of 5000 and mix 40 is 10,000. Fair-Rite's 31
> material has a relative permeability of 1500.
>
> Digikey carries several sizes of toroid cores in mix 35 and 40 at
> moderate price. Search DigiKey's web site for 35T or 40T to see what
> they have available. For example, a 1 inch OD core is $1.19 in single
> lot quantities. Smaller cores, 0.54 inch OD, are 23 cents each in single
> lot.
>
> Steward's 35 and 40 material are MnZn ferrites and will have dimensional
> resonance in the HF frequency range, with the exact frequency depending
> on the core dimension. I suspect that dimensional resonance won't be an
> issue for a current choke at your frequency range, however. Fair-Rite
> claims the 31 material, although also a MnZn ferrite, does not have
> dimensional resonance. Type 43 is a NiZn ferrite and does not have
> dimensional resonance in the HF frequency band.
>
>
> Jack K8ZOA
>
>
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