Message	Date	From	Subject
9753	2014-02-15 10:35:36	Biastee	Re: Digest Number 2082
Without a magnetic core to concentrate the flux, is the toroid's self-shielding still preserved? Nevertheless, the paper's sputter and mill method of constructing the windings looks like a viable solution to the problem of automated toroid winding. If shielding is not necessary, then Toko MC119 and MC122 ferrite slug tuned coils are capable of similarly high Q in the VHF range. Chin-Leong, 9W2LC
9754	2014-02-15 11:03:46	Thomas S. Knutsen	Re: Digest Number 2082
This is an interesting question, toroids with low AL value will radiate more than high AL value cores. An fully wound core would reach the expected AL and therby consentrate most of the fields inside the core. With low turns one will see that the Al value will be higher than the published value for low AL cores, and the inductance will be higher than the calculated value. This is due to lekage fields not coupled to all the windings. In order to determine the approximate field contained inside the core, one can wind an 1:1 transformer on the core, and measure the K factor. For 43 material ferrite I measure > 98%, while for -10 and -0 iron cores I regulary measure around 68%, depending on coverage of the core. These measurments are fairly easy to do, you measure the inductance with the transformer connected aiding (series) and then oposing (parallell). Then the K factor will be: K = (la/lo-1) / (la/lo +1) But, since the windings with the approach of sputtering on Cu (or even Au or Ag) would cover the whole core, all the fields should be constrained inside, but then there is the slots needed in order to make the windings that may radiate. I think the toroids described may be worth doing some experiments with, does anyone want to set up an sputter deposition chaimber (requires vacuum) and an plating line? 73 de Thomas LA3PNA. 2014-02-15 8:22 GMT+01:00 Biastee <biastee@yahoo.com>: Without a magnetic core to concentrate the flux, is the toroid's self-shielding still preserved? Nevertheless, the paper's sputter and mill method of constructing the windings looks like a viable solution to the problem of automated toroid winding. If shielding is not necessary, then Toko MC119 and MC122 ferrite slug tuned coils are capable of similarly high Q in the VHF range. Chin-Leong, 9W2LC

This is an interesting question, toroids with low AL value will radiate more than high AL value cores. An fully wound core would reach the expected AL and therby consentrate most of the fields inside the core. With low turns one will see that the Al value will be higher than the published value for low AL cores, and the inductance will be higher than the calculated value. This is due to lekage fields not coupled to all the windings.

In order to determine the approximate field contained inside the core, one can wind an 1:1 transformer on the core, and measure the K factor. For 43 material ferrite I measure > 98%, while for -10 and -0 iron cores I regulary measure around 68%, depending on coverage of the core. These measurments are fairly easy to do, you measure the inductance with the transformer connected aiding (series) and then oposing (parallell). Then the K factor will be: K = (la/lo-1) / (la/lo +1)

But, since the windings with the approach of sputtering on Cu (or even Au or Ag) would cover the whole core, all the fields should be constrained inside, but then there is the slots needed in order to make the windings that may radiate.

I think the toroids described may be worth doing some experiments with, does anyone want to set up an sputter deposition chaimber (requires vacuum) and an plating line?

73 de Thomas LA3PNA.

2014-02-15 8:22 GMT+01:00 Biastee <biastee@yahoo.com>:

Without a magnetic core to concentrate the flux, is the toroid's self-shielding still preserved? Nevertheless, the paper's sputter and mill method of constructing the windings looks like a viable solution to the problem of automated toroid winding.

If shielding is not necessary, then Toko MC119 and MC122 ferrite slug tuned coils are capable of similarly high Q in the VHF range.

Chin-Leong, 9W2LC