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     Northam, Western Australia
     QRZ Page: VK6YSF

 

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TOROIDAL FERRITE CORE TYPES

Recommended core types for various frequency bands and power levels.


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Summary of suitable ferrite cores and core types for a frequency range of 100 kHz to 50 MHz for power levels of 50W, 100W, and 500W continuous and SSB. It assumes good thermal management and proper balun design.

 

Type 43 is versatile for HF but heats up quickly at higher frequencies.

Type 61 is ideal for upper HF and VHF, with lower losses at higher frequencies.

Average Power: SSB power is typically 25-30% of PEP, allowing smaller cores or fewer stacked cores to handle the same PEP compared to continuous modes.

 

Frequency Range

CW Power

SSB Power

Core Type

Recommended Core(s)

Notes

100 kHz–1.5 MHz

50W

150w

Type 31

FT-140-31

Type 31 is best for low frequencies due to lower core losses.

100W

300w

Type 31

FT-240-31

Larger core ensures better heat dissipation for higher power.

500W

1500w

Type 31

2 × FT-240-31

Stacked cores improve power handling. Ensure proper cooling.

500W

1500w

Type 75

2 × FT-240-75 

Type 75 is optimized for lower frequencies, but larger cores may be needed for high power.

1.5–10 MHz

50W

150w

Type 43

FT-140-43

Type 43 is sufficient for moderate power with proper ventilation.

100W

300w

Type 43

FT-240-43

Handles most HF applications at this power level.

500W

1500w

Type 43

2 × FT-240-43

Requires cooling for continuous duty cycles.

 

500W

1500w

Type 61

2 × FT-240-61

Type 61 offers better performance for higher frequencies within this range.

10–20 MHz

50W

150w

Type 43

FT-140-43

Adequate for low power, but heat buildup limits performance.

100W

300w

Type 43

FT-240-43

Effective for low to moderate power levels.

 

500W

1500w

Type 43

2 × FT-240-43

Requires active cooling for high power.

 

500W

1500w

Type 61

2 × FT-240-61

Preferred for higher frequencies within this range.

20–30 MHz

50W

150w

Type 43

FT-140-43

Limited performance at the upper HF band. Upgrade to Type 61 for efficiency.

100W

300w

Type 43

FT-240-43

Works well for most HF applications.

500W

1500w

Type 43

3 × FT-240-43

Higher core count manages heat from increased losses.

500W

1500w

Type 61

3 × FT-240-61

Better efficiency at upper HF frequencies; good for continuous duty.

50 MHz (VHF)

50W

150w

Type 61

FT-140-61

Type 61 is ideal for VHF with low core losses.

100W

300w

Type 61

FT-240-61

Larger core ensures higher power handling at VHF.

500W

1500w

Type 61

3 × FT-240-61

Stacked cores reduce heating; active cooling recommended.

500W

1500w

Type 31

3 × FT-240-31

Type 31 can be used, but core losses will be higher at VHF compared to Type 61.

 

 

Efficiency Comparison at 50 MHz

 

A Type 61 balun can achieve 90–95% efficiency at 50 MHz, while a Type 43 balun may only reach 50–70% due to core losses and heat dissipation. The difference becomes more pronounced at higher power levels.

  

Parameter Type 43 Core Type 61 Core
Operating Frequency Range ~1 MHz to ~30 MHz ~10 MHz to ~200 MHz
Core Losses High (inefficient at 50 MHz) Low (efficient at 50 MHz)
Efficiency (%) ~50–70% (varies with power) ~90–95%
Power Handling Lower due to heating Higher due to lower losses
Heat Generation Significant at moderate power Minimal at moderate power
Bandwidth Narrow at 50 MHz (reactive losses dominate) Wide at 50 MHz

Data Source: ChatGPT 4.0

  

 

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Page initiated 09 December, 2024 

Page last revised 15 December, 2024

 

 

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Mode: Mode: FST4W 300 (Similar to WSPR)

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