Toroid material differences

[Wendymott]

Hi peeps.
Looking at the Toroid data sheet @ Toroids . info...... there is a nice table and calculator for various types and dimensions.
What is the difference between a FT xxx type and a T type please...... I guess one is Ferrite and the other is something else
Typically a FT50/43 @ 2 mhz with a required inductance of 37uH = 9.2 turns... while a T50/1 at the same requirement is 60 turns.

This inductor is required for the series Vcc supply choke for a Topband PA.

Over to you
Regards
Wendy G8BZY

[Radio Wrangler]

The amateur radio fraternity picked up a range of toroid cores being sold by Bill Amidon, Otsego street, Hollywood. He put his own stock numbers on the cores.

So By FT cores most people refer to ferrite cores made by Fair-Rite inc in Wallkill Noo Joisy - but renumbered by Bill's shop. Bill put the Fair-Rite material number next and his code for the size. Fair-Rite's part number is a bit more complex. Material number 43 is a well known Fair-Rite Ferrite that is good for HF transformers and becomes an EMC absorber above 100MHz

By T-cores, most people refer to the dust iron cores (higher Q and more stable L than ferrite) which Bill bought from Micrometals inc of Anaheim California (Home of Disneyland and Robert Heinlein but not actually a fictional place) The appended number like the '2' in T50-2 is the iron mix number in the Micrometals catalogue.

Amidon is just a distributor/retailer so the same cores are available under their actual manufacturer's part numbers from a variety of outlets.

David

[Wendymott]

Hi David. So you are saying the FT toroids are ferrite and would offer a higher permeability but less stable as in power handling, where as the "T" toroids have less permeability but are more stable and able to handle more power.
Which accounts for the massive disparity in turns required for a value of inductance.
I have a reasonable collection of large toroids and beads removed from SMP's.... which I guess are Ferrite, as they seem to have a larger permeability.
Its a pity that recycled cores are seemingly anonymous.... as they would be in production.

[Radio Wrangler]

Major problem.... trying to identify cores if the source isn't known.

You have several sorts of dust/carbonyl iron powder cores
Quite alot of different ferrites which are quite different to ferrites
And you get stuff like powdered mumetal for even more inductance.

Arnold Engineering did some low freq powdered metal cores that got used in period SMPS filters.

David

[G0HZU_JMR]

One other issue with the FT50-43 ferrite toroid is that with 9 turns on it I think it will be prone to saturation if you pass dc current through it that approaches 1A.

I dug out an old works spreadsheet and entered the dimensions of the FT50-43 toroid and the initial permeability of 800. It predicts an Al of 440 and this predicts an inductance of about 36uH with 9 turns. However, the spreadsheet also predicts that there will be a degree of saturation if 1A dc current is passed through it. This means that if it was used as a PA choke the impedance of the toroid would change depending on the current passing through it. It might not matter for some applications like a low power topband PA but the inductance and ESR will change (at 1.9MHz) depending on the current through the toroid. The impedance of the powdered iron toroid will be much less affected by dc current.

From memory there are also two versions of the 43 material and they have slightly different curves on a complex permeability vs frequency graph. So this can muddy things a bit if you use an older 43 material toroid and compare it to the latest datasheet.

The little nanovna would be a useful tool if you wanted to compare the small signal impedance vs frequency for the FT50-43 and the T50-1 based inductors.

[Radio Wrangler]

Also a PA DC feed choke is operating in a relatively low impedance environment and you don't need as much inductance as you'd guess. This helps a bit on the saturation front as you either need fewer turns or a lower permeability core.

David

[Wendymott]

Thanks David and Jeremy ... I keep forgetting the usefulness of the VNA. Its one of those bits of equipment I bought thats in the cupboard..should be "out" on prominent show.
I now have some FT50-43's in my stock, to complement the T50's