Propagation

The radio can be excellent and the path can still say no.

The changing path

Solar flux, sunspots, flares, geomagnetic activity, absorption, season, time of day, terrain, antenna pattern, local noise, and frequency all shape what is possible.

Primary sources

NOAA Space Weather Prediction Center NOAA SWPC products NOAA radio communications ARRL propagation resources

What belongs here next

Live space-weather panels, K-index, solar flux, flare and absorption products, eclipse observations, band notes, and dated operating reports can be added after the source, accessibility, and failure behavior are tested.

Terrain and elevation still matter.

VHF and UHF discussions should begin with antenna, height, terrain, and path before escalating immediately to repeaters and linked systems. A repeater is powerful infrastructure when it is located where it can repeat something useful.