Friday, 3 June 2011

UK Propagation charts for June 2011

We’ve seen some massive swings in the solar flux index over the last few weeks, from around 80 up to 112. The authors of VOACAP (the basis for HamCap, which is used to produce the charts) always recommend that you use the smoothed or rolling average sunspot number for its predictions, which is what I always do. That’s why the charts are based on what can look like a low sunspot number when compared with reality. The smoothed number is supposed to give the best overall result, although experience tells us that the actual conditions can vary dramatically from one day to another. Conditions on 21MHz and higher will be dominated by Sporadic E (Es) events rather than F2 layer for the next couple of months, so expect to see short-skip openings on these bands (as well as 14MHz) even though the charts suggest that no propagation may be possible. As always, keep an eye on to view the latest solar flux index (SFI) and K index, which may be a better short-term indicator of conditions as a raised K index will suggest CME and coronal hole activity that could adversely affect HF. Being logarithmic, a rise from a K index of one to four doesn’t sound like much, but certainly is. As the K index is updated every three hours it is a good indicator. The non-logarithmic A index is an average of the last 24 hours so often doesn’t reflect events that have occurred in the last few hours. Don't forget the free ebook on LF and HF propagation - see right. Go to the UK HF propagation charts for June

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