RSGB Propagation News - 14 December 2025
We had a bit of everything last week, including increased Kp indices, a high solar flux, an X-class solar flare and coronal mass ejections.
The solar flux index hit a maximum of 220 on Thursday, 4 December. This brought good HF conditions until Sunday, 7 December. The index declined to 169 on Thursday, 11 December, which was still more than enough to excite the ionosphere.
We had an X-class solar flare at 0501UTC on Monday 8 December. This originated from large active region 4298, which has now rotated out of view. We also had more than ten M-class solar flares over the past week, showing that the prediction of disturbed conditions on the downward part of the solar cycle still holds true.
The Kp index hit 6.33 on Wednesday, 10 December, which disrupted maximum usable frequencies, or MUFs. The net result was that digisonde traces were missing at times, with the MUF over 3,000km being in single figures on Thursday, 11 December.
To cap it all, we now have a very large Earth-facing coronal hole that threatens HF propagation today, 14 December.
There has been DX around, but mostly on the lower bands. CDXC’s Slack group reports that KP2B on St Croix was worked on the 80m band using FT8 on the morning of Thursday, 11 December. TO9W on St Martin was logged on the 40 and 30m bands using CW on Tuesda,y 9 December. TT1GD in Chad also appeared on the 40m and 20m bands using CW on Monda,y 8 December.
Next week, NOAA predicts the solar flux index will be in the 130 to 140 range. However, as was mentioned earlier, geomagnetic conditions may be disturbed today, 14 December, due to a fast solar wind stream from a coronal hole.
Conditions might calm down from the 15 to the 20 December, before the Kp index hits 5 around the 21 to 26 December.
In summary, get your HF DXing in during next week, before auroral conditions take their toll over the Christmas period.
VHF and up propagation news from G3YLA and G4BAO
The present period of unsettled weather will remain the driving force for weather conditions for most of the country for the period up to Christmas.
This will mean that there are likely to be some very windy spells with extensive rain and squally showers. It offers scope for rain scatter operators on the GHz bands, but scarcely any hint of good tropo conditions.
One item of interest is the meteor scatter prospects from the Geminids, which peak today, 14 December. It is one of the busiest showers of the calendar with a peak hourly rate of 120, so it should provide plenty of opportunities and is worth exploring during the week before and following the peak.
The solar conditions have again remained interesting enough with a red alert on the evening of Wednesday 10 December, and there is always the potential for the Kp index to produce signs of auroral radio activity once it goes above 5.
Finally, a reminder that this winter period, from mid-December to mid-January, can produce some surprisingly effective Sporadic-E. It’s possibly easiest to see by checking the propquest.co.uk graphs to
see if the foEs trace is showing any sharp spikes.
The 10 and 6m bands are probably the more likely bands to show signs of activity in these winter events, but it’s certainly worth checking if the graphs show any promising signs.
For EME operators, Moon declination went negative on Friday 12 December, meaning shortening Moon windows and decreasing peak elevation. We are past perigee for the month, so path losses are increasing. 144MHz sky noise starts low but increases to high by Friday 19 December when the Sun and Moon are close in the sky.
https://rsgb.org/main/blog/news/gb2rs/propagation-news/2025/12/12/propagation-news-14-december-2025/
(Alan Pennington, UK/BDXC)
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