[Amps] Silly Inductor Question

[George KB2Z]

Stack the cores. 2 or 3 end to end.
George


At 09:11 PM 2/7/05 -0800, you wrote:

>Suppose that I want an inductor of 5 mH that will handle 1500 watts into a
>3:1 SWR from 1.8 to 30 Mhz (to build an L network antenna tuner, at the
>output of a solid state amplifier, say).
>
>12 turns on a T-400A-2 powdered iron core will give me something like 5.2 uH
>at a maximum flux density of 70 gauss at 500 volts at 1.8 Mhz (with no DC
>current flowing).  70 gauss is acceptable at 1.8 Mhz (and it gets better
>relative to the spec as you get higher in frequency).  Fine, I'm a happy
>camper.
>
>Now suppose that I want an inductor of .5 mH, all else the same.  4 turns on
>the same core gets me .58 mH, close enough - but the flux density is now
>210, well beyond acceptable limits.  Things get worse for smaller inductors
>- the flux density goes through the roof for just 1 or 2 turns.
>
>I can't buy a bigger core easily - so what do I do?  Is my only option an
>air core inductor (which I then have to shield...)?  It seems more likely
>that I am being dense, as usual :-)
>
>Thanks!
>
>                         ***dan, K6IF
>
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