We present one the method of determining HF propagation conditions on a particular path.
This is a complex subject, but a simple method is to to be found on this site.
This is a web based version of the VOACAP program originally devised by the international broadcaster Voice of America.
Full instructions for use may be found here but, for normal use, it is only necessary to "drag and drop" the red symbol on the map (the transmitter QTH) and the blue symbol (the receiver location). Set the transmitter power and select antennas from the lists. Select the modulation type.
Current sun spot number is updated automatically in that program but for completeness it, and various other indices are tabulated below.
Updated 19 December, 2015