Ferrite Materials for RF Chokes, Baluns & Filters
Explore our curated range of high-quality ferrite toroids for building baluns, ununs, common-mode chokes, and EMI filters. Stocked in popular sizes (FT114, FT140, FT240, and more) and trusted mixes (31, 43, 52, 61, 77) to cover everything from LF/MF and low-band HF through VHF/UHF. Ideal for amateur radio, RF labs, and EMC-critical designs.
Quick Selector — Mix vs. Band & Typical Use
| Mix |
Best Frequency Range |
Typical RF Use |
| 31 |
~0.1–10 MHz (effective up to ~15 MHz) |
Low-band HF/LF common-mode chokes, mains/EMI suppression |
| 43 |
~5–50 MHz |
HF common-mode chokes, 1:1 baluns/line isolators, UNUN cores |
| 52 |
~20–200 MHz |
Upper-HF to VHF chokes and matching transformers |
| 61 |
~50–500 MHz |
VHF/UHF transformers, broadband matching, low-loss RF inductors |
| 77 |
~0.02–2 MHz |
LF/MF chokes, audio/IF transformers, low-frequency EMC |
Ranges are indicative; optimal performance depends on turns count, wire type, stack count, and intended impedance target.
Sizing Tips
-
Core size vs. power: FT240-class is the go-to for 100 W–1.5 kW HF line isolators and 49:1/64:1 transformers; stack 2–3 cores for higher dissipation margin.
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Impedance target: For HF CMCs, aim for >5 kΩ from the lowest band of interest up to ~30 MHz; adjust turns/stacking to raise impedance without over-heating.
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Wire & insulation: Use PTFE or high-temp magnet wire and maintain spacing at high RF voltage points (e.g., EFHW transformers).
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Thermal headroom: If ferrite warms noticeably during long transmissions, increase stack count or switch to a more lossy mix in the problem band to boost CMRR.
Build Notes
- Distribute turns evenly around the core; avoid bunching to reduce stray capacitance.
- For multi-band chokes, mix count & spacing often matter more than absolute turns.
- Keep leads short and route return conductors tightly coupled to minimize loop area.
