[Towertalk] Measuring/ calculating Inductance

[Red]

Hi, Steve and all;

ARRL handbooks provide formulas and graphs for calculating inductance and designing coils.

>From the 1994 handbook:

"The approximate inductance of a single layer air-core coil....

L = d^2 times n^2) ÷ (18 times d + 40 times l)

where:
L = inductance in microhenrys
d = coil diameter in inches (measured to outside diameter)
l = coil length in inches (measured to greatest length)
n = number of turns
(d^2 = d squared and n^2 = n squared)

This formula is a close approximation for coils having a length equal to or greater than 0.4d."

The handbook presents several graphs and tables to simplify the calculations for coils of selected diameters and turns per inch.

Hope this helps.

73 de WOØW

ve6wz_steve wrote:

> I am looking for some advice or references on how to calculate and/or measure the inductance of a loading coil.  I have been modelling a loaded yagi (for 80m) and know the reactance I require for the loading coils, and want to design the coils.  I have experimented with a coil on a 6 '' form and have tried to measure the inductance with my MFJ analyser....the MFJ will not measure over 650 ohms reactance.  Is there another way to either accurately measure the inductance or calculate the winding required for "Y" inductance using "X" gauge wire on "X" diameter form?  I realize experimentation will ultimately be required but I'd like to get close on my first design.
>
> de steve VE6WZ.
>