Toroids, RF-Cores

by Tony van Roon

Toroids & RF-chokes, come in different shapes and sizes, like in donut, tube, and stick models, and are used on a large scale in a variety of electronic equipment. Toroids can be of different materials, like Ferrite or Iron. The most common application today is filtering. If you check your cable at the back of your computer monitor you will find one, or even two, on the cable going to your computer. They are also used in Power Supplies, Radio, Ham Radio, Scanners, Transmitters, Transformers, and Electro-Magnet applications.
Here is an excellent link to provide more 'Amidon' information: Bytemark Inc.

Below I have made up 3 tables with the most common-size toroids. I hope they can be of some assistance to you. The 'µ' stands for the permeability factor of the core.

Red E Cores

The photograph at left shows a Toroid Red 'E' Iron core and is used in a CW-transmitter (morse-code) application in the 30-meter band.

Still Under Construction!!!