On 10/07/2010 13:50, RussellMc wrote:
>
> However/also, it seems to me that an air wound core will also be achievable
> that works OK.
> This page contains an apparently superb calculator that goes beyond the
> simplistic formula that I offered.
>
>                http://hamwaves.com/antennas/inductance.html
>
> How good it is is uncertain, and what the target R is is unknown to me, but
> it seems that 4 to 6 turns of eg 15mm silver plated copper tube wound in a
> (tight ) 100 mm dia spiral with minimum inter turn clearances will produce
> inductances of the order required. Resistances appropriateness need checking
> but are probably bearable.
> They give what seems to be AC resistance (ie skin effect modified
> resistance) but I haven't even tried to check for reasonableness.
Sounds like the correct ball park from my experience of high power HF 
"Tank circuits".

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