[HomeBrew] Pros and cons of stacking toroids in an HF high power application?

[John Marshall]

Ray,
Most formulas hams use for toroid inductance are based on an Al value, usually expressed in microhenries per turns-squared. If we dig a little we can come up with a more general formula based on the core's dimensions and permeabilithy. Here are a couple of sources:

< http://www.ferronics.com/files/Toroid.pdf >
< http://www.phys.uri.edu/~gerhard/PHY204/tsl267.pdf >

The bottom line is that for cores with a rectangular cross section, like the ones we typically use, the inductance is directly proportional to the core height (thickness). So for a given number of turns, stacking two cores gives twice the inductance as a single core, three cores, three times the inductance, etc.

My experience is that a little super glue will hold the cores together and make the winding easier. Just don't glue your fingers together!

John, KU4AF
Pittsboro, NC

On Aug 19, 2014, at 2:38 PM, Ray, W4BYG wrote:

> I have searched about a dozen of my library references plus online, for definitive info on the above and find little or nothing.  None of the available toroid calculators that I have allow me to double the cores.  Can anyone elaborate on the subject or recommend an online site?
> 
> 73,
> Ray, W4BYG