RF PropagationHFIonosphereVHF/UHF

Electromagnetic Wave Propagation Modes

Radio waves don't just travel in straight lines — they can bounce off the sky, hug the ground, or bend around obstacles. How they travel depends on their frequency.

Propagation Cross-Section
Earth cross-section showing ground wave (green), sky wave via F-layer (amber), and line-of-sight with Fresnel zone (blue)
D layer (day)E layerF layer (HF skip)Fresnel zoneReflectionTXRXGround waveSky waveLine of sight
Propagation Mechanisms

Dominant Propagation Mode by Frequency Band
Quick reference for which propagation mechanism dominates in each band
VLF / LF (3–300 kHz)
Ground wave + waveguide (Earth-ionosphere)
MF (300 kHz–3 MHz)
Ground wave (day), sky wave (night)
HF (3–30 MHz)
Sky wave / ionospheric skip
VHF (30–300 MHz)
Line-of-sight, sporadic-E, troposcatter
UHF (300 MHz–3 GHz)
Line-of-sight, ducting, satellite
SHF / EHF (3–300 GHz)
Free-space LOS, rain/gas absorption
Related Tools
Put these concepts to work

Path Loss Calculator

Calculate free-space path loss for line-of-sight links

Fresnel Zone Calculator

Find the clearance needed above obstacles for LOS links

Link Budget Calculator

Complete system-level analysis including propagation losses