Dan Petersen's
professor coyle
Spider Web Version

    Professor Coyle's Spiderweb Coil Calculator WIRE TABLE:  
          GAUGE W =
      (FORM INSIDE DIAMETER) I.D. =   12 0.086
      (NUMBER OF TURNS) N =   14 0.069
      (WIRE DIAMETER) W =   16 0.056
          18 0.040
          20 0.035
          22 0.029
        RESULTS:   24 0.022
      (INDUCTANCE) L(uH) = Uh   26 0.018
        COIL O.D. = inches   28 0.014
        FORM O.D. =  inches   30 0.011
      AMOUNT OF WIRE NEEDED =  feet    
      (COIL SPREAD) b =      
      (MEAN RADIUS) r =      
    The result is a theoretical value. The actual will be slightly different.    
      With an inductance of microhenries,    
      and a capacitance of picofarads,    
      your  tuned circuit will resonate at megahertz.    
      The reactance (both Xc & Xl) at megahertz is ohms.
              Note: Closewound coils will resonate at a slightly lower frequency.      
Instructions for Professor Coyle:

Professor Coyle is intended to be a mathematical aid in determining the inductance of a coil and the resonant frequency of a coil-capacitor tuned circuit.

Spiderweb calculator:

The original Spiderweb calculator was designed by Charlie Cotterman and artwork added by Dan Petersen. To use the calculator, enter the required information in the indicated area in the red number area. The calculator will give you the results indicated by the blue text in the results column. Looking at the representation of the spiderweb form, you will note that the dimensions you need are in the dimension lines.

To Use the Resonance Calculator:
Enter the known inductance and capacitance into the calculator section at the top of the page. The resonant frequency and the reactance of the L-C circuit will be given in blue immediately below. Example: You have a 40-400pF variable capacitor and a 240uH inductor and you want to find the tuning range. Enter the inductor value, press <enter>, and the highest variable capacitor value into the calculator and press <enter>. You should see a resonance of .514 MHz. Left-click on the capacitance value and now enter 40. You should now see a resonance of 1.624 MHz. In this example would be perfect for tuning the AM broadcast band.The result is a theoretical value. The actual frequency will differ slightly due to distributed capacitance and measurement tolerances.

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