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Old January 5, 2017, 06:36 PM   #129
Unclenick
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Join Date: March 4, 2005
Location: Ohio
Posts: 16,400
Like you, I've got a dated B-K LCR meter sitting in the basement. You remind me it's been so long since I had it and a number of other meters and various pieces of equipment out, that I should double-check that I've pulled all their batteries. I should also take all the vacuum tube equipment and other line powered gear out and give it AC in gradual steps with a Variac to let the electrolytic capacitors re-form their oxide layers.

I'll bet the old single-layer cylindrical air core coil formula put into Excel will come close enough to give you a good design basis for your substitute coils. I'm sure you have it, but for others reading, it is:

μH = (nr)² / (9r + 10l)


Where
μH is inductance in microhenries
n is the number of turns
r is the mean radius of the coil (¼(ID + OD)) in inches
l is the length of the coil in inches

It is generally credited with about 1% accuracy, which is better than the capacitor tolerances are likely to be.
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