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27/5/16

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HF Propagation

Steve G0KYA, the Chairman of the RSGB's Propagation Studies Committee, has updated his hourly UK HF Propagation Predictions maps for the rest of 2016.
You can view the charts using the link from g0kya.blogspot.co.uk
These take into account the latest smoothed sunspot numbers from NOAA/NGDC.
Steve says: “We continue to see a steady decline in sunspot activity as we fall away from the peak of solar cycle 24. Twelve months ago the solar flux index peaked at 163 in May. This month it has struggled to exceed 100 and is currently 94.
“Coupled with this, we have suffered quite badly from the effects of plasma from solar coronal holes. These are areas of the sun with an open magnetic field that allows plasma to escape.
“If these coronal holes are earth-facing the result can be an elevated K index as the plasma from the high-speed solar wind stream impacts the earth, especially if it has a negative or south-facing magnetic field, which couples more easily.
“A high K index is usually a sign of poor HF conditions, with noisy bands and depressed maximum usable frequencies. Any path over the poles is also badly affected.
“This can also lead to aurora, which while not being visible in the summer, can lead to openings on VHF,” Steve said.
He said that looking further ahead it doesn't look too good for next weekend's RSGB HF CW National Field Day (June 4 and 5) as plasma from a recurring solar coronal hole could push the K index up to five. This may see the HF bands become noisy and maximum usable frequencies fall away if the current predictions are correct.
Apart from occasional short-skip sporadic E openings on 10m, the highest “money” band for Field Day is predicted to be 20m, with some possible openings to the southern hemisphere on 15m.
Forty metres should also give consistent openings around Europe, with DX being workable at night. Eighty metres may give good openings around Europe after dark, but is unlikely to yield much DX.
Steve said that the Propagation Studies Committee is also pleased to be able to present its latest HF propagation prediction tool, which is currently hosted at www.predtest.uk
This is still being developed and uses the newer ITURHFPROP software as its backend, rather than VOACAP.
“We encourage amateurs to use the system, which can also be used for point-to-point predictions using a prototype tool called 'Proppy',” Steve said.
Gwyn G4FKH, who is project manager for the new system, welcomes feedback. Steve said the goal is for the whole system to be moved to the RSGB website once finished.
• All propagation reports can be found at:
http://www.southgatearc.org/propagation

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