Ferrite Toroids, Cylinders for Balun, RFI Control, Feedline CM Current Choking

Ferrite Toroids, Beads

Ferrites are made to different component formulas ( typically known as mix's ), to provide desired characteristics. There is no magic "one type fits all". Below is a table that provides a guide to some of the common mixes used in Ham Radio, and the use / frequency range over which they are most applicable. The 'mix' numbers are "Fair-Rite" brand - other manufacturers may use identical mix numbers but the product characteristics may differ.

Mix #	EMI Suppression	Transformer	Comment
31	1-300 MHz	1:1 only, < 250 MHz	Ideal for antenna feedline chokes at lower HF Ham bands. OK for current baluns - not suitable for voltage baluns other than 1:1.
43	25-300 MHz	3-60 MHz	Generally more economic that mix 31, but suited to higher HF Ham bands when used as a common mode choke.
61	200-2000 MHz	1-300 MHz	Lower loss therefore useful for voltage transformers where power is transferred via magnetic flux
73	0.1-10 MHz	< 10 MHz	Low frequency EMI suppression - good choice for SMPS noise reduction.
75	0.15-10 MHz	0.1-10 MHz	Good choking impedance at low frequencies - good choice for SMPS noise reduction.