Toroids - Ferrite
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. |
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Ferrite Core, Mix 75, Cylinder, 1.02" OD, 0.5" ID, 1.125" Long
Fair-Rite p/n 2675102002Offers high choking impedance at low frequencies. DimensionsODIDHeightm..
$3.20 Ex Tax: $2.78
Ferrite Core, Binocular, Mix 61, 1.062" Long, 0.525" Wide, 0.295" High. BN-61-6802
Fair-Rite p/n 2861006802, Mix 61 core suitable for suppression applications >250 MHz or 1 -..
$2.50 Ex Tax: $2.17
Ferrite Core, Clip On, Mix 31, 0.25" ID
Clip-on split core suitable for RG58 Coaxial CableMix 31 offers useful choking in the HF and lower V..
$5.00 Ex Tax: $4.35
Ferrite Core, Clip On, Mix 31, 0.5" ID
Clip-on split core suitable for RG8 / LMR400 Coaxial CableMix 31 offers useful choking in the HF and..
$8.90 Ex Tax: $7.74
Ferrite Core, Cylinder, Mix 31, 0.687" OD, 0.375" ID, 1.125" Length
Fair-Rite p/n 2631665702Offers useful choking impedance at HF through VHF frequencies for a single t..
$2.40 Ex Tax: $2.09
Ferrite Core, Cylinder, Mix 75, 0.687" OD, 0.375" ID, 1.125" Length
Fair-Rite p/n 2675665702Offers high choking impedance at low frequencies.DimensionsODIDHeightmm17.49..
$2.80 Ex Tax: $2.43
Ferrite Core, FT-140-43, Toroid, 1.4" OD, 0.9" ID, 0.5" High
Fair-Rite p/n 2643802702Commonly used in Amateur Radio HF antenna feedline common mode current choke..
$4.20 Ex Tax: $3.65
Ferrite Core, FT-140-61, Toroid, 1.4" OD, 0.9" ID, 0.5" High
Fair-Rite p/n 5961002701Mix 61 Toroid suitable for HF transformer (voltage balun) service...
$6.10 Ex Tax: $5.30
Ferrite Core, FT-240-31, Toroid, 2.4" OD, 1.4" ID, 0.5" High
Fair-Rite p/n 2631803802 Mix 31 Toroid, commonly known as FT-240-312.4" size suitable fo..
$16.40 Ex Tax: $14.26
Ferrite Core, FT-240-43, Toroid, 2.4" OD, 1.4" ID, 0.5" High
Fair-Rite p/n 2643803802 Mix 43 Toroid, commonly known as FT-240-432.4" size suitable fo..
$11.50 Ex Tax: $10.00
Ferrite Core, Mix 43, Bead, 0.38" OD, 0.197" ID, 0.19" High
2643002402 (Fair-Rite)Ferrite Bead for upper HF ~ VHF EMI suppression.Typically used in multip..
$0.15 Ex Tax: $0.13
Ferrite Core, Mix 73, Bead, 0.38" OD, 0.197" ID, 0.19" High
2673002402 (Fair-Rite)Ferrite Bead for lower frequency (< 50MHz) EMI suppression.Typically ..
$0.30 Ex Tax: $0.26
Ferrite Core, Oval Toroid, Mix 43, 1.53" Wide, 1.025" High, 1.125 long
Fair-Rite p/n 2643167851, Mix 43 core - ideal for multi turn coaxial cable HF chokes.=> Article b..
$7.40 Ex Tax: $6.43
Ferrite Core, Toroid, Mix 75, 1.22" OD, 0.748" ID, 0.591" H
Fair-Rite p/n 2675821502, Mix 75 toroid suitable for lower frequency EMI controlDimensionsODIDHeight..
$3.60 Ex Tax: $3.13