Propagation News – 30 April 2017

Last week saw some unsettled conditions due to the effects of a coronal hole. Its associated high speed solar wind stream actually hit the Earth a day earlier than predicted, resulting in poor HF conditions during the International Marconi Day event on Saturday, 21 April.

The planetary K-index hit six the night before and we were left with noisy bands and poor propagation. HF openings were predominantly to Europe, although Australia and the US were worked by GB0CMS from Caister in Norfolk. While conditions improved slightly through the week the K-index remained steadfastly high.

There were highlights though. The A25UK Expedition to Botswana was worked from the UK on bands as high as 10 metres. As this is a North-South path, signals didn’t have to go through the unsettled auroral oval.

There were a couple of sunspots that helped push the solar flux index to more than 80, but next week NOAA predicts the SFI will be around the mid to high 70s, with unsettled geomagnetic conditions at times. The K-index could hit five on Bank Holiday Monday, but then decline to three or four for the rest of the week.

We should soon start to see the start of the sporadic E season, which may bring good short-skip opportunities on the upper HF bands. Keep an eye on the 10 metre beacons from around 28.150 to 28.330MHz for openings.

VHF and up

Low pressure will bring showery rain into western Britain later in the weekend, with prospects for GHz bands rain scatter. This will soon be replaced by a ridge of high pressure extending south from a large high over Scandinavia. The ridge may bring the possibility of some tropo conditions towards the east across the North Sea.

That said, the quite strong easterly wind over southern areas may not be the best for good tropo, since it is likely to be a dry flow and thus there may not be a good moisture contrast between the surface and the dry air above any temperature inversion. If tropo turns out to be not such a strong player, there are good reasons to hope for some sporadic E as we move into the first week of May. This is usually regarded as the start of the main sporadic E season, so the main periods to check are late morning and late afternoon.

As we said earlier, start with 10m and then move higher in frequency as any opening develops. The openings can eventually reach 2m.

Moon declination is high and losses still low this weekend but declination falls and losses increase as the week progresses.

A week today, before dawn, the Eta Aquarids meteor shower peaks, but the shower’s radiant never gets very high above the horizon for observers in the Northern Hemisphere.

Category: GB2RS Propagation News