spiral pi coil

[dbanner]

N represents the number of turns off wire
At the bottom of the page there is a flat spiral formula with diagram
This formula good for the ballpark, close to your target inductance. Good enough for rough calculations that will give reasonable results. The gauge of wire 0.4 to 0.6mm not so critical to the outcome, very small difference it makes.
Microhenries for L but inches for other parameters, not that metric system rubbish
The table on the left is used to find no of turns per inch for any gauge of wire, good to know for arriving at value of b in formula. Should be able to transpose formula for solving number of turns required given other parameters. Old school, yes.

[6666]

Any chance you could show a picture of your coil so we know what we are dealing with ? those figures dont sound right

[sinclairuser]

hi all i have tried to make a flat spiral coil, it is outer dia 14cm, inner dia 1cm, 35 turns.
it reads 0.04 mh and 0.9ohms, its wound out of .6mm bell wire but reads 0 cap.
so i'm not convinced its right, does anyone have a good spiral coil calculator, the ones ive found seem to be useless, or want to install stuff on my computer.
thanks,
aly.