HF Propagation Calculator

Estimate Maximum Usable Frequency (MUF), optimum frequency, and hop count from solar flux index, time, distance, and season.

Solar Flux Index (SFI)

Time (UTC)

Target Distance

Season

Tab to move between fields

Max Usable Frequency (MUF)

14.17 MHz

Optimum Frequency (FOT)

12.05 MHz

Lowest Usable Freq (LUF)4.72 MHz

Critical Frequency (foF2)14.13 MHz

Hops Needed2

Total Hop Loss16 dB

Max Single Hop3,956 km

Sec(θ) Factor1

Recommended Band20m (14 MHz) or 17m (18 MHz)

How to Use This Calculator

Enter the current Solar Flux Index (SFI) from WWV, DX bulletins, or propagation websites.
Set the UTC time, path distance to your target (km), and current season.
Review the Maximum Usable Frequency (MUF), Optimum Working Frequency (FOT), and LUF.
Select frequencies at or below the FOT for reliable propagation on this path.
Account for foF2 critical frequency and estimated number of ionospheric hops needed.

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Formula

MUF = foF2 × sec(θ); FOT = 0.85 × MUF

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