All Slip On Ferrite Beads
Ferrite beads are used for RF decoupling and parasitic suppression. When placed over a wire, cable or coaxial cable they suppresses common mode current flowing on the wire or wire bundle or the outside of the coax shield but does not affect the signal inside the coax cable or wire (differential current).
For RFI common mode suppression use, mix 31 is effective from 1-300 Mhz, mix 43 works from 25-300 Mhz, Mix 61 is for 200-2000 Mhz, and mix 77 favors .1-50 MHz.These frequencies are those of the interfering signal to be eliminated, not the operating frequencies of the equipment to be protected. See Mix Selection for other applications.
SNAP ON Sizes for Heliax and Coax Cable
Shown below in the table are the SLIP ON and SNAP ON products for various popular Heliax and Coax cables. These are the correct size for making sleeve chokes – See above table for technical details.
There are two basic ferrite material groups: (1) Those having a permeability range from 20 to 850 µ are of the Nickel Zinc (NiZn) class (mix 43,61,67), and (2) those having permeabilities above 850 µ are usually of the Manganese Zinc (MnZn) class (Mix 31,77).
The NiZn ferrite cores exhibit high volume resistivity, moderate temperature stability and high ‘Q’ factors for the 500 KHz to 100 MHz frequency range. They are well suited for low power, high inductance resonant circuits. Their low permeability factors also make them useful for wide band transformer applications.
The MnZn ferrite cores, have permeabilities above 800 µ, have fairly low volume resistivity and moderate saturation flux density. They offer high ‘Q’ factors for the 1 KHz to 1 MHz frequency range. Cores from this group of materials are widely used for switched mode power conversion transformers operating in the 20 KHz to 100 KHz frequency range. These cores are also very useful for the attenuation of unwanted RF noise signals in the frequency range of 2 MHz to 400 MHz and above.
A Ferrite Mix Selection Guide is available HERE for aid in choosing the proper mix for your application. Available popular mixes include 31, 43, 61, 67, and 77