The IARU supports, with a small annual grant, a worldwide network of HF beacons known as the International Beacon Project (IBP). The beacons were constructed by volunteers of the Northern California DX Foundation (NCDXF) and operate from 18 locations on the following frequencies on a time-shared basis: 14.100, 18.110, 21.150, 24.930, and 28.200 MHz. The NCDXF/IARU beacons help both amateur and non-amateur HF radio users assess the current condition of the ionosphere.
Additional beacons operate just above 28.200 MHz and normally are coordinated by regional IARU Beacon Coordinators.
Except for short-term experiments such as observation of the effects of solar eclipses the IARU does not support the operation of amateur beacons below 14 MHz because of congestion in these bands.
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