Propagation News – 5 August 2018

The solar flux index stayed around the 70 mark last week, although a new tiny sunspot did become visible on Tuesday. Unfortunately this had little real effect on the SFI, although it did push the sunspot number to 11. This can be misleading due to the way sunspot numbers are calculated. You score 10 for each group and one for each sunspot, so the leap from zero to 11 only means one spot has appeared.

We got the geomagnetic forecast correct last week, as conditions were quite settled. As many amateurs found in the IOTA contest, HF conditions were largely average, with a predominance of European signals. However, there were reports of some intercontinental DX, especially for better-equipped stations.

Next week, NOAA predicts the solar flux index will be pegged at 68, although we think it could rise a little above this due to the sun’s active region. The other news is another active region is heading around the sun and its effects may impact us in around a week’s time.

Geomagnetic conditions this week will be largely settled, but with the possibility of a slightly raised K index this weekend due to an equatorial coronal hole. Expect HF conditions to continue pretty much as they did in July, with daytime maximum usable frequencies over a 3,000km path struggling to exceed 14MHz at times.

In Doctor Tamitha Skov’s weekly solar forecast on YouTube she said the new sunspot region could push conditions to the “top end of poor”, which sums up solar minimum! You can find out more about her work at www.spaceweatherwoman.com

The IOTA contest showed that there is still Sporadic-E activity around on 14-28 MHz, but it sometimes takes a contest to get people to take advantage of it.

Finally, as we are now into August you should be using the new smoothed sunspot number of five with your VOACAP-based prediction programs.

VHF and up

There is a distinctly Tropo look about the weather charts this week as high pressure remains the dominant feature across the British Isles and nearby continent. This type of pattern can produce some long-lasting openings across the length of the high on the charts, preferably along one side rather than directly across the centre of the high, since this is where the inversion sinks very low and the duct can easily be cut short by high ground.

There will be a slight hiccup around mid-week in the south as a weak area of low pressure disrupts the high, bringing a risk of thundery showers to southern parts of the UK. It could mean a chance of rain scatter on the microwave bands though.

Sporadic-E isn’t over yet, but the position of jet streams do not look favourable. There is almost a total absence of Sporadic-E-producing jet streams within mainland Europe, except in a fairly limited band across northern Britain and the north Atlantic, so check the beacons and the clusters to find out which paths are open.

We are approaching the peak of the Perseids meteor shower around the 12th August so meteor scatter paths will be good either side as it is a broad peak.

This is a good week for EME as the moon is heading back towards its closest point to Earth, perigee, on August 10th. It also reaches maximum northerly declination on August 8th. Note that the sun and Moon are close on Saturday morning, meaning high sun noise.

Category: GB2RS Propagation News