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From: Ed Burke
Date: 2/27/00
Time: 1:09:59 AM
Remote Name: 207.57.42.134
I'm new at radio, so just for practise I tried to check the inductance of the coil Hue described: 42 turns on 2.5" diam. form, length 8". In searching the Web for formulas, I found two that give very different numbers.
N = number of turns A = diameter of coil B = length of coil C = depth of winding (assumed to be 0)
http://www.icorp.net/users/kev/tesla/formula.htm
L = (N*A)^2 / (9*A + 10*B)
Gives 105.5 microhenries.
The other is at
http://www.uslink.net/~cybercir/cir23.htm
L = 0.2 * (N*A)^2 / (3*A + 9*B + 10*C)
(This one has been in the ARRL Handbook for many years.)
Gives 27.7 microhenries! That would certainly explain why Hue couldn't make it tune the BCB.
Would someone advise which one (if any) is correct?