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Propagation News – 12 September 2021

What a difference a week makes! Last week we were looking at a virtually spotless Sun and we said that NOAA predicted the SFI would decline into the low 80s. But this week we have had an explosion of sunspot activity. As a result, the SFI has gone up to 100 with a sunspot number of 87. Just to recap, that doesnt mean that there are 87 sunspots, as groups count for 10 and sunspots count for one. In any event, it shows that the cycle is progressing nicely.

The solar wind pushed the Kp index up to four on Wednesday, but this didnt seem to impact MUFs too much.

HF conditions are definitely improving, probably by a combination of seasonal changes and the increased solar flux. There were extensive openings to South America and the Caribbean this week on 21MHz and we can expect these to improve as the month goes on. It was good to work the Dominican Republic on 15m FT8 as well as numerous Brazilian and Argentinian stations. It will be interesting to see if we get 10m openings to North America in late September, which normally requires an SFI of more than 100 to make them reliable.

Next week NOAA predicts the SFI will reduce to around 85 again as active regions 2863 to 2869 rotate out of view. There are signs of another group that will come into view, but we may not get the high SFI that we have experienced this week. The good news is that geomagnetic conditions are likely to remain settled due to a lack of coronal holes, as long as we dont get any coronal mass ejections.

VHF and up:

For newer licensees, last weekend was possibly the first experience of a decent Tropo opening coinciding with a major European SSB/CW contest. The European 144MHz contest showed what the band is capable of, without the help of a computer, with SSB QSOs from Scotland down to the Czech Republic.

This week on VHF and above its very much a little bit of Tropo, a little bit rain scatter, and a little bit flat band. The weekend is seeing the end of the unsettled conditions with high pressure returning for a while for the start of the new week. A couple of further showery incursions and rain in the northwest around midweek and just a hint that further high pressure ridging may return at the end of the week. So in terms of propagation interests it feels like a mix of Tropo and some GHz rain scatter at times, with periods of no particular preference, and of course always a small chance of some aurora or meteor scatter, so keep your options open.

Random meteor activity is still high and the September Epsilon-Perseids are still active until the 21st of September, so keep checking in the early morning for the best MS conditions.

With the Moon at minimum declination on Tuesday, peak moon elevations drop to 11 degrees and the Moon is only above the horizon for around six and a half hours. It reached perigee on Saturday so path losses will be low but increasing. (

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