> Somewhere there must be a formula for the inductance of a hand-wound
> coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

Reply by amdx●August 20, 20192019-08-20

On 8/20/2019 9:07 AM, Peter Percival wrote:

> Somewhere there must be a formula for the inductance of a hand-wound coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

If your getting into crystal radio,
You might find this interesting,

> Somewhere there must be a formula for the inductance of a hand-wound coil.
>
> Air core, one layer of wire (of given swg) close-wound, diameter of
> former (cardboard, probably inside of toilet paper roll), length of
> coil,... (what else?), therefore inductance equals ...

Yep a dozen.
I have spreadsheeet labeled the Nagaoka Formula that is supposed to be
very accurate. You can search for it, But I think these use his formula,

That's enough so you will never know who is correct :-)
I ecpect
The ones I have used is Professor Coyle, and I had a downloaded version,
so haven't tried the online version and electronbunker.
Mikek

Reply by default●August 20, 20192019-08-20

On Tue, 20 Aug 2019 15:07:07 +0100, Peter Percival
<peterxpercival@hotmail.com> wrote:

>Somewhere there must be a formula for the inductance of a hand-wound coil.
>
>Air core, one layer of wire (of given swg) close-wound, diameter of
>former (cardboard, probably inside of toilet paper roll), length of
>coil,... (what else?), therefore inductance equals ...

of course there are. Your google is broken?
BTW single layer solenoid-wound coils usually hit the calculate values
spot-on, it doesn't start to get hairy until you add layers. There's
a formula that takes into consideration the diameter/length ratio too,
but for simple single layer coils try the "Amateur Radio Handbook."

Reply by Peter Percival●August 20, 20192019-08-20

Somewhere there must be a formula for the inductance of a hand-wound coil.
Air core, one layer of wire (of given swg) close-wound, diameter of
former (cardboard, probably inside of toilet paper roll), length of
coil,... (what else?), therefore inductance equals ...