sabato 26 giugno 2021

Propagation News – 27 June 2021

We had another week that was largely dominated by Sporadic-E openings. It is worth pointing out that Sporadic-E can and does have a blanketing effect on HF signals, which can prevent them from reaching the F2 layer of the ionosphere. This means that predictions created by a program like VOACAP or ITURHFPROP can often be over optimistic. VOACAP and ITURHFPROP do not take into account seasonal Sporadic-E and, in any event, the localised and changing nature of Sporadic-E clouds means it would be very hard to make monthly median predictions.

During the summer months, take computerised propagation predictions with a pinch of salt. While short-skip propagation may be better at times, longer distance signals may in fact be worse than the predictions.

Sunspot region 2833 has now rotated out of view off the Sun’s edge and we can expect the solar flux index to decline from the 80 reached on Thursday. The good news is that at least two returning regions, 2830 and 2831, will be turning back into view over the weekend. A lack of coronal holes means geomagnetic conditions should remain quiet over the next week. NOAA predicts the solar flux index will be in the range 76-78 with a maximum Kp index of two.

Lastly, due to a major outage at the server in the States at the University of Massachusetts Lowell, there is no ionosonde data on the website foF2 graphs at the moment. The server has been subjected to a cyber attack and restoration of the academic services rightly takes priority; the graphs will be there as soon as the server is back online.

VHF and up:

It’s another week of mixed fortunes for VHF/UHF users, with a tendency for high pressure over northern areas after the unsettled weather moves through during the tail end of this week. It eventually leaves an area of low pressure close to, or over, southern areas and this remains in place for much of the next week. Towards the end of the week another low will drift south across eastern areas.

The best chance of Tropo is over Scotland and Ireland, while unsettled and potentially thundery weather will be a good source for some rain scatter activity in southern areas.

The Sporadic-E prospects are looking a bit quiet at first, but as a new upper-low moves into southern UK and France we should see prospects improve again into next week, particularly for paths to Iberia and the eastern Mediterranean.

Moon declination goes positive again on Friday, so peak Moon visibility windows and peak elevations will increase. Path losses will rise throughout the week.

The June Bootids meteor shower peaks today.