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Re: Windings vs. Diameter - errors

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Just to follow up...

My new coil's "official numbers" are:

Diameter 3.000 inches (center to center of wire)  (Starrett #120A-6)
Wire diameter 0.0116 with insulation (Starrett #436-1)
985 turns (electronic counter during winding)
11.500 inches long (Starrett #120-12)
Lexan coil form with Envirotex coating. Lexan end caps with none ferrous end terminals.

DC resistance (HP34401A) = 83.30 ohms

Medhurst inductance = 16.988mH
MandK inductance = 17.088mH
JAVATC (Ldc)= 17.155mH
B&K meter = 17.06mH
Elenco meter (LCR-1801 very trusted) = 17.40mH
Wavetek 37XR = 17.35mH
HP 33120A, 34401, TEK TDS312, Standard cap = 17.47mH

I'll go with the Elenco at 17.40mH since it is always right ;-))


At 300kHz, I am getting in Rac of 196 ohms "in series" with the 83.3 ohms of DC resistance for a total of 279 ohms. MandK predicts 238 ohms, but I am not sure if that is total resistance or just the AC part. But there are a lot of error details with this measurement.