On Apr 14, 2005, at 10:22 PM, Dan Levin wrote:
> I'm trying to design a coil that will be used in a 1500 watt filter at
> HF.
> I know that I need to allow for frequency related skin effect that will
> reduce the area of the wire or tubing carrying the current.
>
> First, I check the ARRL Handbook and the Antenna Book. No formula and
> no
> table showing suggested wire sizes for a given frequency and power
> level.
>
> Next, I determine that the skin depth at 28 mHz is .0005", and I
> calculate
> the copper volume that the current is traveling through at one skin
> depth in
> wires and tubes of various sizes. I get results that seem
> unreasonable -
> using a current density of 2500 amps / square inch I get a current
> capacity
> for #14 wire at 28 mHz of under .5 amps and for 1/2" tubing of just a
> couple
> of amps. Yes, I realize that the skin depth is one standard
> deviation, but
> even allowing for that the capacities seem very low.
E. F. Johnson rated its #14 gauge Cu roller coil at 3A @ 30MHz.
>
> Can someone point me at either a formula or a table that will tell me
> or
> allow me to calculate what the current capacity of a wire or tube is
> at a
> given HF frequency? Or, I suppose to put it differently since the
> capacity
> is related to the acceptable temperature rise - something that will
> tell me
> the copper loss in a piece of wire or tubing at a given frequency?
>
> Thanks!
>
> ***dan, K6IF
>
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>
Rich Measures, 805.386.3734, AG6K, www.somis.org
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