The coil diameter uses the mean diameter of the copper coil.

A 1mm wire wound on a 14mm bobbin will have a mean diameter a bit over 15mm.
The bit over is the uncoiling that naturally occurs when one releases the tensioning force.

I use >=1.6mm diameter enameled copper wire and prefer to use 2.12mm wire wound onto an AA battery.
My mean diameter is roughly 16.9mm
9¾ Turns gives ~1uH

I love the idea that you have Pi to 50 digits. But. It is false precision in the wire length because the length depends on the Turns Per Inch as well. The true length of the line is the length of the hypotenuse of the triangle formed from the true circumference and the turn spacing. It is an error larger than the diameter of an electron, but I think I can live with your formula! ;-))

I just came across this site. I ran some numbers when designing the shunt for my HiQ antenna and found yous to be more accurate than others. My SWR was good without but I wanted to get rid of some unwanted wind noise on digital modes in the especially in the 20 meter band. I used the center of the coil “(ID+OD)/2” which was 37.6mm x 32mm x 10.5 turns. The wire is #8 (3.2mm) dia. My first calculations were less but when I measured it I got 3.1 µH. Yours calculated 3.146. The other calculators I tried online were estimating from 2.2 to 2.8 µH. The wire was some common copper ground wire I picked up at a local hardware store.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish.AcceptRead More

Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.

Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.

Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.

LOVE YOUR CALULATOR……NOT SURE WHEN I NEED TO USE IT….I AM A HAM VIRGIN….BUT LEARNING…..

THANKS A BUNCH

LARRY

Re: Air Cored Inductor Calculator

Hi, Is the coil diameter measured outside, at the middle or inside of the coil ?

Rgds/ 73

Arto Salo

OH1ID

Hi.

I never use thick enough wire to worry, but I would use the inside diameter.

73, John.

The coil diameter uses the mean diameter of the copper coil.

A 1mm wire wound on a 14mm bobbin will have a mean diameter a bit over 15mm.

The bit over is the uncoiling that naturally occurs when one releases the tensioning force.

I use >=1.6mm diameter enameled copper wire and prefer to use 2.12mm wire wound onto an AA battery.

My mean diameter is roughly 16.9mm

9¾ Turns gives ~1uH

Is it possible to add a field for the copper wire diameter?

And use that to calculate the coil resistance in ohms?

Perhaps that would be better as a separate calculator.

What is the meaning of Coil Diameter and Coil length?

Diameter is how wide the coil is and length is how long the coil is.

hi tanx for you helping amateur radio in all of the world

i used of air core calculator.

best regards from Tehran-iran

amirhosein 73

A good approximate formula (accurate enough to 1%) is:

L = (n . d)(n . d)/l x 10^{-10) Henrys , where n is number of turns, d is diameter in mm, l is length in cms,

I love the idea that you have Pi to 50 digits. But. It is false precision in the wire length because the length depends on the Turns Per Inch as well. The true length of the line is the length of the hypotenuse of the triangle formed from the true circumference and the turn spacing. It is an error larger than the diameter of an electron, but I think I can live with your formula! ;-))

Very good Bennett! 🙂

I just came across this site. I ran some numbers when designing the shunt for my HiQ antenna and found yous to be more accurate than others. My SWR was good without but I wanted to get rid of some unwanted wind noise on digital modes in the especially in the 20 meter band. I used the center of the coil “(ID+OD)/2” which was 37.6mm x 32mm x 10.5 turns. The wire is #8 (3.2mm) dia. My first calculations were less but when I measured it I got 3.1 µH. Yours calculated 3.146. The other calculators I tried online were estimating from 2.2 to 2.8 µH. The wire was some common copper ground wire I picked up at a local hardware store.

Good job on the calculator.

Robert N9NQ