How to Calculate Air Core Coils

Hobbysists and radio amateurs sometimes face problem in finding standard value inductors for RF projects.Besides,if someone wants to wind their own inductor they might face problem.Here we will discuss how to calculate and wind air core (or sometimes called coreless) inductors.This types of inductors are generally used in HF and VHF circuits.We generally use the equation below for getting the number of turns needed in our inductor.

N=rot[L(9a+10b)/a] ........ (1)

Where:
N is the number of turns
L is the inductance in micro henry(uH)
a is the coil radious in inches
b is the coil length in inches
rot= squire root of
How to wind:
If you need a small value inductor then just take a pencil or 6mm drill bit or what you get at hand.Then measure its radious in inches.Take a piece of copper wire and make sure that it will pass the current without problem.Then assume a logical length of the coil.At last if you know the inductance just put all data in equation (1) and you will get the number of turns required.It is very easy,isn't it?