Propagation News – 5 July 2015

| July 3, 2015

As predicted, this week the sun has been more settled. The solar flux index has been around the 100 mark and the Kp index has not risen above three. Nevertheless, we are still in the summer HF doldrums and apart from sporadic E openings on the higher HF bands conditions remain fairly lacklustre.

The optimum bands for working the east coast of the US from the UK this week will be 20 or 17m during the day, and 20m or 30m at night. Paths to Japan will be similar. Propagation to South America and South Africa will be better, with openings up to 10m at times.

As we are now in July please ensure you use the latest smoothed sunspot number of 55 for your VOACAP-based prediction programs.

Next week looks like it could potentially be more unsettled with a number of sunspots rotating into view. Three distinct groups will be directly in line with Earth and the potential for flares and coronal mass ejections remains high. NOAA says we can expect the solar flux index to be in the range 125-130, with unsettled geomagnetic conditions on the sixth to the eighth, and again on the eleventh and twelfth.

VHF and up propagation news

High summer is a good time for tropo paths to develop overnight as a strong surface temperature inversion forms. This favours coastal stations for paths across the North Sea, English Channel and down to the south across Biscay towards Spain and the Azores/Canaries. Hot dry air from the continent drifts out across the cool sea surface, providing the mechanism to alter the refractive index.

Inland stations should be aware that inland locations will lose these ‘lifts’ once the temperature rises after dawn. In the coming week, a ridge of high pressure will extend from the Azores high up to southern Britain, so these tropo paths are mainly going to favour the southern half of the country.

Sporadic-E took a bit of a dip last week, but we are still in the main season so have an early look at 10m beacons to determine which paths might open up on 6m, 4m and 2m later in the day.

Last week saw some severe thunderstorms that provided rain scatter contacts in for the southeast on the GHz bands. The likelihood of this is much lower in the coming week due to the high pressure. There are no significant meteor showers this week.

Category: GB2RS Propagation News