Based upon observed propagation in the past hour, and updated at 40 minutes past the hour. NVIS is best just below the highest frequency which the ionosphere will reflect vertically. This is called foF2. The foF2 measurements from ionosondes around the world are used to create this world map. Based Upon Hourly Ionosphere Soundings All maps are updated at 40 minutes past the hour; click on the maps to zoom and reload.
Maps of DX and Regional Optimum Frequencies Based on the previous hour of observed propagation Optimum Frequency Maps Centered on World Cities To use the maps below, locate a map for a city near your QTH and click on it. Follow the color frequency contours to locate an area you wish to communicate with. For optimum signals, tune your radio to the ham band closest to the MHz of the color range indicated by the map. Updated at 40 minutes past the hour; Click on the maps to zoom and reload.
San Francisco
Boulder
Kansas City
Washington DC
Whitehorse
Montreal
London
Rome
Stockholm
Tokyo
Sydney
Darwin
Perth
Auckland
These maps are made from data gathered in real time around the world using HF ionospheric radar systems called ionosondes. Ionosondes bounce HF radio signals off the ionosphere to measure the height of the reflective zones and signal strength vs frequency. The maps are generated using the ionosonde data to make projections based upon a base station working a mobile. Mapping source: Australian Government IPS Radio and Space Services
