![]() Real-time Global D-Layer Absorption map from NOAA space weatherĮ (above D) and F (highest) layers stay in place day and night. LUF (Lowest Usable Freq) means any Freq below this value will be completely absorbed by the D layer. (longer waves) hit more free electrons which in turn hit more air molecules due to air density at low altitudes. So for 10m operation during the daytime, its best to have small D layer and a large F layer.ġ60m-40m band during the daytime may be absorbed (in part or all) by the D layer The D layer absorbs RF at the low end (mostly up to 10mhz) of the HF spectrum (high end HF passes through). The air density is high at the D layer, but the free electron density is actually low due to high rate of recombination of electrons. ![]() Each layers properties is explained below in the following sections.Ĭhecking Propagation based on current Radio contacts and plotting them on a world map (DXMAPS.COM)Ĭhecking Propagation based on Tropospheric Ducting Forecast ()ĭ (lowest) layer mostly appears with direct Sun (Ultraviolet radiation), but can also occur due to hard X-Ray emissions during a Solar event. ![]() But the density of free electrons and their height determine whether RF photons gets absorbed, refelected, or passes through. These free electrons can act as a mirror to the RF photons from your radio waves. The Ionosphere layers responsible for HF Propagation Space Weather - HF Radio Wave Propagation
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