Propagation News – 8 August 2021

The last week looked like we were back at solar minimum again! With the solar flux declining to 71, and the sunspot number at 14 on Thursday, it hardly looks like things are improving. This was coupled with news from NASA that they have revised their projections for Solar Cycle 25.

NASA heliophysicists at the High Altitude Observatory, based at the University Of Colorado, now predict the peak of Solar Cycle 25 will top out at a value of 195, plus or minus 17. This is based upon the new scale for calculating smoothed sunspot numbers. For reference, Solar Cycle 21 peaked at an SSN of 233 on the new scale, while Solar Cycle 23 peaked at an SSN of 180 on the same scale. They also now agree that the dramatic run-up in sunspot activity we experienced late last Autumn was an outlier. In other words, they are saying that Cycle 25 may not yet have properly started. Or at least, we are not seeing a dramatic start, but only time will tell if they are right.

Maximum useable frequencies remain subdued, partly because of the low solar flux and partly because we are still in the summer doldrums. With the daytime critical frequency mainly in the range 5 to 6MHz, this means the 40m band remains closed to near-vertical incidence skywave or short skip. Daytime MUFs over 3,000km struggle to get much above 18MHz.

Laurie, G3UML reports OA4DX in Peru has been CQing on 30m using CW around midnight, nice if you fancy working a fairly rare one. Thirty metres can be a good band after dark if you like digital modes or CW.

Amateurs looking to work around the UK during the day are better off looking at 60 metres, the 5MHz band, or perhaps just waiting until nightfall when the absorbing D-layer dissipates and 80m comes alive.

There is a chance of unsettled geomagnetic conditions across this weekend, thanks to a high-speed solar wind from a coronal hole.

Next week NOAA predicts that the solar flux index will remain in the mid-70s. Geomagnetic conditions look set to remain mainly quiet, apart from a period around August 10th and 11th when the Kp index may rise to four.

So, in conclusion, we think the main message is to make the most of any Sporadic-E as the season is now past its peak. And if you want to work DX stay as high in frequency as you can during the day, perhaps 17 or even 15 metres, or look at 30m and 40m after dark for some occasional surprises.

VHF and up

The basic pattern of unsettled weather looks like continuing into the coming week. This means that rain scatter QSOs should be worth a look for the GHz operators. It is hard to see any significant Tropo coming out of this weather pattern except perhaps for a time around the middle part of the week when high pressure to the south of Britain may give some Tropo conditions from southern areas into the continent.

The other mode of choice, even in August, is still going to be Sporadic-E and this spell of unsettled weather is very good for providing strong summer jet streams, which can be important in the formation process of Sporadic-E. Overall, the positioning of the jet streams looks better at the end of this week and into the beginning of next week, whereas later next week the jet stream strengths will probably be weaker.

As we move into the middle of August, the peak of the Perseids meteor shower is approaching in the second half of the week. This is potentially good for Sporadic-E, since meteors are the source of the ionisation comprising Sporadic-E, but obviously also a good thing for meteor scatter activity. Thursday the 12th and Friday the 13th sees the peak of the shower, so with a ZHR of 100 and some big fireballs, not only will MSK144 and FSK441 digimodes produce excellent results with modest stations, fast CW and SSB with slick operating will also bring QSOs for those larger stations.

Moon declination goes negative next Thursday so Moon windows will shorten as the week progresses. Perigee is still nearly a fortnight away, but path losses will continue to decline.

Category: GB2RS Propagation News