Ham Radio Propagation Calculators
Ten propagation calculators covering Maximum Usable Frequency, skip distance, free-space path loss, link budget, grey line timing, Fresnel zone clearance, radio horizon, ERP and EIRP, solar flux index interpretation, and take-off angle vs. distance. All run in your browser.
MUF from Critical Frequency and Path Distance
Estimates the MUF for a given ionospheric critical frequency (foF2) and path distance. Also shows the Lowest Usable Frequency and the best operating frequency (85% of MUF).
Ionospheric Skip Distance Calculator
Minimum skip distance for a given frequency and ionospheric layer — the "dead zone" closer than the first skip return. Also shows maximum single-hop range.
Free-Space Path Loss (Friis Formula)
Signal attenuation between two isotropic antennas in free space. The baseline for all radio link budget calculations.
HF Link Budget Calculator
Estimates received signal strength and SNR for an HF path given TX power, antenna gains, path loss, and noise floor.
VHF/UHF Radio Horizon Calculator
Maximum line-of-sight range between two VHF/UHF stations given their antenna heights. Includes 4/3 Earth radius atmospheric refraction correction.
Fresnel Zone Radius Calculator
Calculates the required obstacle clearance (60% of first Fresnel zone) for a VHF/UHF path to avoid significant diffraction loss.
Grey Line Time Calculator
Approximate sunrise and sunset times for any longitude, and the enhanced propagation window on the grey line (day-night terminator) for low-band DX.
Solar Flux Index (SFI) Band Conditions Estimator
Interprets the 10.7cm solar flux index (SFI) to estimate which HF bands are likely to support ionospheric propagation and typical foF2 values.
ERP, EIRP and Equivalent Power Calculator
Converts between transmitter power, antenna gain, feedline loss, ERP (referenced to dipole) and EIRP (referenced to isotropic). Shows equivalent power comparisons.
Required Take-Off Angle for a Given HF Path Distance
Estimates the required elevation take-off angle for a single-hop ionospheric path to a target distance. Useful for optimising antenna height for DX.