RSGB
GB2RS News Team | August 15, 2025
Last weekend was characterised by unsettled geomagnetic conditions caused by a massive coronal hole on the Sun.
At one point, the Kp index got up to 6, with a corresponding decrease in maximum usable frequencies, or MUFs. In fact, the Dourbes Digisonde failed to record much at all over a six-hour period. Luckily, that disruption had passed by Monday, 11 August, as the ionosphere started to get back to normal.
Meanwhile, the solar flux index reached a peak of 153 on the 10 August, before dropping back to 140 on Thursday the 14 August. There have been numerous C-class solar flares and ten M-class events over the past five days, but nothing of note.
The MUF over a 3,000km path exceeded 24.9MHz at times, but has generally been between 21 and 24MHz.
Another coronal hole is Earth-centric at the moment and could cause some disruption, with increased Kp indices by tomorrow, the 18 or Tuesday, 19 August.
HF DX has been good at times with the stand-out station being T30TTT in Western Kiribati. The station has been worked on many bands, including 20, 15 and 10m using CW, as well as FT4 and FT8. After two weeks there will be just one operator who is there until mid-September. So you have plenty of time to work him.
Stanley, AH6KO, in Hawaii, has also been spotted on the 15m band using CW. This is a relatively rare opportunity and good for anyone chasing their Worked All States award.
A little closer to home is Henri, OJ0JR on Market Reef who has been easily workable on the 30m band using FT8. Get in quick though as he is only there until tomorrow, the 18 August.
Next week, NOAA predicts that the solar flux index will remain in the
140 to 150 range. Unsettled geomagnetic conditions are forecast for tomorrow, the 18 August, until Wednesday 20 August, probably caused by the coronal hole mentioned earlier. Better conditions are predicted for the 23 to the 27August with a maximum Kp index of 3.
VHF and up:
Last week’s propagation highlights were SSB and CW QSOs between the UK and Las Canarias on both the 23 and 13cm bands between G4GLT, EA8DMF, ED8BRZ and EB8AYA.
There may be more Tropo next week with high pressure close to, or over, the British Isles. However, at this time of the year, any Tropo will be due to temperature inversions. These can be at the surface and are especially persistent over water, so look for marine paths across the North Sea or up the east coast to Scotland.
Other potentially good marine paths might be across the Channel or Biscay to Spain and beyond. The hot days of high summer break down these surface inversions over the land during the day so, if your station is inland, your best chances of Tropo in summer will often be overnight and until mid-morning.
Inversions can also be elevated in the region of the high pressure, say between 1 and 2km above ground, giving good DX prospects that are not affected by the heating of the summer day. In this high-pressure period, it is much more likely to be a surface inversion that drives the Tropo.
There will be little rain in prospect except for parts of Ireland, South Wales and southwest England, where a few thundery showers are possible.
However, these will not be particularly good for rain scatter.
There continue to be some aurora alerts so monitor the Kp index and if it is rising to, say, 6 try beaming north on the 10, 6, 4 and 2m bands in turn to see if any genuine auroral signals are coming back.
Lastly, the Sporadic-E season is coming into its closing weeks. 10m is a good band to check first. If Sporadic-E is very short-skip there, try moving up to 6m or beyond for a strong event. Digital modes are best, so use these to get clues as to where the CW and SSB paths might show up next.
Meteor scatter operators have been very busy during the Perseids meteor shower. The Perseids should still provide some activity into the coming week.
Moon declination is positive and rising until Tuesday 19 August, so Moon window lengths and peak elevation will follow suit. Path losses are rising again as we are now past perigee. 144MHz sky noise is low to moderate all next week.
