Propagation News – 3 September 2017

Last week saw the solar flux index climb into the high 80s. Our prediction that the weekend’s ionosphere might be unsettled was partly correct, as the effects of a coronal hole pushed the K index to three on Sunday, but this quickly recovered. We are now seeing a shift from predominantly summer ionospheric conditions to autumnal. As the ionosphere starts to cool it experiences a shift away from predominantly diatomic molecules to more monatomic species. These are easier to ionise and, as a result, we can expect to see better conditions and potentially higher maximum usable frequencies as we move into September and October.

Roger, G3LDI reports that 15 metres was open to the US on Wednesday afternoon, which bodes well for the future. And G0KYA’s tests with 5W and WSPR on 20 metres resulted in him being picked up in Alaska around UK sunset, which was also very positive.

Now the bad news. A very large coronal hole on the Sun threatens to push the K index higher this weekend as a high speed solar wind impacts the Earth. This may result in noisy bands and suppressed MUFs, which could impact this weekend’s HF SSB Field Day operations.

NOAA predicts the solar flux index will be in the low to mid 70s next week. Once the coronal hole effects die away we may then get some more settled conditions. Either way, keep an eye on HF as you might be pleasantly surprised.

And now the VHF and up propagation news.

The end of the main Sporadic-E season is approaching rapidly now and, despite some 6m and 4m openings last Wednesday to Eastern Europe, such events will become much rarer in September. Check the beacons on 10m and perhaps 6m, but in general it’s back to meteor scatter for DX on the lower VHF bands now.

The prospects of Tropo should improve as we head into the quieter mellow days of autumn and high pressure becomes more commonplace. We should see a ridge of high pressure lasting until mid-week when the patterns flip to become dominated by low pressure. This means that Tropo will be worth investigating at first and with the ridge extending over much of the country most parts of the UK will get something out of this period. The changeover to low pressure-dominated weather patterns from mid-week is less useful, although if there are any significant spells of heavy rain or thundery showers, then rain scatter on the GHz bands is a possibility.

At this time of the year, very humid ex-tropical moisture from the States can become part of the train of low pressure systems that cross the Atlantic and make heavy rain more likely.

There are only minor meteor showers this week, so continue to look around dawn for the best random meteor scatter contacts

Moon declination is increasing again, going positive on Friday. Losses fall and Moon windows get later and longer as the week progresses, with the best operating times very late at night or early morning.

And that’s all from the propagation team this week.

Category: GB2RS Propagation News