Propagation News – 7 August 2022

Last week was characterised by a solar flux index around 100, but reasonably settled geomagnetic conditions. The SFI had a low of 94 on Sunday and a high of 100 on Thursday. The Kp index has been in the range of one to four, with more settled conditions being experienced in the second half of the week.

Daytime critical frequencies have ranged from lows of 5MHz and highs of up to 7MHz. As a result, skip distances on 40m have varied dramatically, and often very quickly. This has caught out some amateurs who have found solid inter-G conditions one minute, but fast fading as the critical frequency has dropped leaving only European stations workable.

As a guide, keep one eye on propquest.co.uk for the current critical frequency and extrapolated maximum usable frequencies over different path lengths. Only then can you make sense of daytime 40m propagation.

Sporadic-E is still putting in an appearance, but is far less prevalent as we head into August. It may still be usable for weak signal modes like FT8, but loud SSB signals from Europe may be less prevalent.

Next week, NOAA’s Space Weather Prediction Centre predicts that the SFI will be in the range 98-100 again. That is, it doesn’t think we will get any rapid increases in sunspot numbers over the next week. The Kp index is forecast to be in the range 2-3, which means moderately settled geomagnetic conditions. However, a coronal hole on the Sun’s equator may cause some problems just after the weekend.

So daytime F2-layer MUFs over 3,000km paths may be up to 18-21MHz. Any short-skip 10m openings are therefore likely to be Sporadic-E.

 VHF and up

The basic pattern continues unchanged with high pressure favouring southern and eastern areas and lows with their fronts affecting the northwest. Occasionally weakening cold fronts drift southeast. This will provide further tropo opportunities, particularly during the hot and humid periods and in this case a good cloud cover near the surface is a good indicator.

The preferred paths would most likely be across the North Sea to Denmark, Germany and Netherlands and across the Channel to the continent. A more extensive option could be to the south across Biscay to Spain and beyond to the Canaries and mid Atlantic. Rain scatter is unlikely for most areas except for very isolated showery developments on the weak cold fronts over central parts of the country.

The Sporadic-E season continues to trickle charge log books with occasional openings. Although the jet stream activity is relatively weak over central and southern Europe, it has been shown that it is sometimes more important that the pattern is moving, however weak.

The stronger flow appears to favour paths across the north of the UK to Iceland and Greenland and towards Scandinavia and the Baltic states. Check the daily blogs on the website which continue through August, for latest thoughts on the daily jet stream charts.

Next week sees the peak of the Perseids around the 12 August and even if you don’t have the gear for meteor scatter it’s hard to beat watching meteors on a warm summer evening. The Sun has continued to exhibit some marked coronal holes, a potential source of the solar wind surges that produces the aurora, so be aware of this.

The Moon passes a milestone this month with perigee and minimum declination coinciding. From then onwards, perigee and maximum declination start to drift closer again, but it’s not until September 2026 that they coincide. All week the Moon elevation is low at zenith and the Moon is only visible for a few hours out of the 24. 144MHz sky noise is high, reaching 3000 Kelvin on Monday.

Category: GB2RS Propagation News