Ferrite cores ain't cheap when you start talking about the 3 inch ID ones. I can see em for like 40 and 50 bucks....
I don't see why I can't just ground a slinky or something.
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1$\begingroup$ We need to know more about what you want to achieve before we can give you a solid answer. $\endgroup$– Brian K1LIApr 3, 2021 at 18:58
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$\begingroup$ It is unclear what you are asking. It can be reopened if you edit your question and tell us more. $\endgroup$– Mike Waters ♦Apr 7, 2021 at 22:30
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A ferrite core used for radio is specially constructed to conduct magnetic fields while not conducting electrical current, especially eddy currents.
A slinky is (typically) an uninsulated conductive coil of variable spacing, and thus variable inductance. It is nothing like a ferrite core. Typically they are made of steel which his high resistance (for metal), although I have seen copper "slinkies" made specifically for radio use.
Ferrite cores are usually priced by size, which is proportional to the power they can handle. A torioidal ferrite with a 3 inch inner diameter is quite large and likely would be heavy and be able to handle a quite large amount of power. Perhaps you can make use of a much smaller one instead? If you need that size for the power, you should be worried about safety, not cost.
Some people have used slinkies as antennas. In this use, they can act like a broadside helical antenna that you can tune by adjusting the spread of the coil. However, as it is not very stable, the tuning will change randomly as it moves around, so this could be a bit of a problem. Also, steel is generally a poor choice for antenna material due to its magnitivity and resistance (although it will work but with lots of resistive loss).
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$\begingroup$ This is a great answer (and therefore it should eventually be reopened); but we have to guess at what the OP meant. :-) $\endgroup$– Mike Waters ♦Apr 7, 2021 at 22:35
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$\begingroup$ Vague questions give lots of room for good answers. $\endgroup$ Apr 8, 2021 at 12:02
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$\begingroup$ Well, there are rules about whether or not vague questions are permitted in Help. $\endgroup$– Mike Waters ♦Apr 9, 2021 at 2:33
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A slinky as in the one you watch go down the stairs? I'd assume not. Any winding on a slinky would probably act as inductor/transformer with an air-core. Ferrites have special magnetic properties. There is a reason they are expensive.
