sabato 9 luglio 2016

Propagation News – 10 July 2016

We got the forecast for last weekend about right. Plasma from a coronal hole hit the Earth late on Saturday, pushing the K-index to four. The solar flux index, however, has remained doggedly in the 70s. DX has been possible on HF though. After a request for information last week Peter, M0RYB said he was pleased to work TR3SA in Gabon on 20 metres on Saturday at 1824Z. He also worked a station in Brazil on 20m.

This week should see the solar flux index remain in the mid 70s as the only visible sunspot on the solar surface rotates away to the south-east. A small coronal hole on the sun’s equator is rotating into a geo-effective position about now, which may mean a geomagnetic storm could hit early next week, perhaps Monday or Tuesday. This may see the K-index rise to four with the corresponding noisy bands, lower maximum usable frequencies and poor polar paths.

Sporadic E continues to give some respite on the higher HF bands. But outside of this the maximum usable frequency over a 3,000km path is struggling to hit 18MHz, with 14MHz being more reliable. The Chilton Digisonde suggests 20m may remain open through the night at times, but 10MHz may be a better option.
VHF and up propagation:

It looks like another week with low pressure, rather than high pressure, on the charts. This will again suggest that there could be some rain scatter options for the GHz bands. The latter part of the week does hint that at a ridge of high pressure temporarily close to southern Britain could offer a small chance of some weak tropo into northern France.

There should still be some sporadic E to liven things up and, since we are seeing such unsettled weather continuing, it suggests that jet stream activity will be on offer again. This is good since these are the sources of the gravity waves or turbulence that can propagate upwards to the E region to help form sporadic E. Most of the time the main jet stream zone will be across the Atlantic into the UK and northern Europe, which favours paths to the Baltic, Poland or Scandinavia, with a later in the day option to North America.

The Moon’s declination goes negative today, with consequent shorter moon windows from early afternoon to late evening. Losses are high, with apogee occurring on Tuesday.