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     Northam, Western Australia
     QRZ Page: VK6YSF

 

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AIR COIL INDUCTOR DESIGN

Air coil inductor design.


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The approximate inductance of a single layer close wound air-coil may be calculated from the below formula.  

 

Where

L = Inductance in µH

r = Former radius in mm

 = Length of winding in mm

N = Number of coil turns

 

Example:

Coil has 20 turns close wound on to a 25mm diameter (12.5mm radius) former and the wire is 1.2mm diameter which will make the overall length of the coils 24mm.  

 

A slightly more practical formula for determining the number of coil turns for a given value of inductance.

 

 

Example:

Required Inductance of 7µH on close wound single layer air inductor with a 25mm former and the wire is 1.2mm diameter which will make the overall length of the coils 24mm.  

 

 

 

The below chart shows inductance in uH of inductors with 7 different former sizes against the number of coil turns.

 

Fig 1 The chart shows inductance in uH of inductors with 7 different former sizes against the number of coil turns.

 

 

Reference http://hamwaves.com/antennas/inductance.html

 

  

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Page last revised 05 May, 2025

 

 

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VK6MJM is a  LF/MF station located in Manjimup, Western Australia.

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