Toroids

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 applications today are filtering, and transformers. 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 4 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. All measurements are given in 'inches'. I don't have or know the info in mm (metric) so don't ask.

Iron Powder Properties: Material 0 1 2 3

Basic-powder Permeability (µ) Phenolic 1 Carbonyl C 20 Carbonyl E 10 Carbonyl HP 35

Freq.Range(MHz) 100 - 300 0.5 - 5.0 2.0 - 30.0 0.05 - 0.5

Color-Code Tan Blue Red Gray

6 7 10 12 15 17 26

Carbonyl SF Carbonyl TH Carbonyl W Synthetic Oxide Carbonyl GS6 Carbonyl Special

8 9 6 4 25 4 75

10 - 50 5.0 - 35.0 30 - 100 50 - 200 0.10 - 2.0 50 - 200 LF Filters,Chokes

Yellow White Black Green/White Red/White Blue/Yellow Yellow/White

*Non Linear: Material #17 was developed as a temperature stable (50) alternative to the #12 (170). Frequency ranges shown are for best 'Q'/Useful over broader frequency ranges with lower 'Q'.

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

Back to Circuits Menu Copyright © 1999, by Tony van Roon Last updated January 8, 2006