By Courtesy of the Propagation team
G3YLA JIM
G0KYA STEVE
G4BAO JOHN
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Jim Bacon G3YLA
NARC club member
and Nick Henwood
RSGB President.
Propogation News
5th December 2025
HF
3
The prediction made for last week was for the solar flux index to increase, possibly reaching 155 by December 1st and 175 by the sixth.
In fact, it hit 196 on the first and 200 on the second. This was no doubt aided by three large sunspot groups in the Sun’s southern hemisphere.
We also said that the Kp index could hit five on December 3rd, and it actually hit 6.67. So well done to the Space Weather Prediction Centre for their forecast.
On Thursday, December 3rd, the solar wind speed gradually increased from around 360 km/s to 475 km/s, thanks to the onset of an enhanced solar wind from a very large coronal hole. The Bz component of the interplanetary magnetic field (IMF) has also been pointing sharply south at times, which means it more easily couples with the Earth and the Kp index goes up as solar plasma floods in.
We expect the geomagnetic disturbance to last at least until Saturday the 6th.
MUFs have been affected, but not too much. The MUF over a 3,000km path was still above 28MHz on December 3rd, at least until sunset. Nighttime MUFs are now characteristically below 14MHz, leaving only 10MHz and below open to DX.
As reported by CDXC’s Slack group this week, DX included the YJ0GC DXpedition to Vanuatu and OX7AM in Greenland on 10 metre CW, 5R8IC in Madagascar on 15m FT4, and SU8YOTA in Egypt on 20m SSB.
Next week, NOAA predicts that the solar flux index will stay in the range 180-190 and the good news is that the Kp index is predicted to remain low, at least until Saturday, the 13th, when it is forecast to rise once again to five.
So get your HF DXing in during the daytime over this coming week!
VHF and up
The weather charts for the coming week or more show a very unsettled pattern with some deep areas of low pressure, strong winds and heavy rain at times.
Tropo is unlikely in the traditional high-pressure sense, but sometimes a strong maritime south-westerly wind can bring a brief slight improvement for parts of southeast Britain in the windy warm sector of the depression, which could be something for this Tuesday, December 9th.
Rain scatter remains a good option since there will be numerous bands of rain and showers available as scatter elements. The Margate 24GHz WebSDR has seen the Flanders beacon ON0HVL for a number of days due to rain over the southern North Sea, but the lack of East Coast active 24GHz stations made this a frustrating watch on a WebSDR.
Aurora is a possibility during the period. Look for a Kp index above Kp=5 to generate a good radio response. The evening of December 3rd saw classic fluttery HF signals on 40m and 80m, supported by a Kp index of 6.67 and reported Auroral QSOs on 144, 70 and 50MHz.
Lastly, a consideration of the meteor scatter prospects is more promising as we are now in the broader period for the Geminids, which peaks on Sunday, December 14th at the end of next week. This shower has a maximum hourly rate of 120 per hour, so ranks as a joint second after the August Perseids.
For EME operators, Moon declination reaches a maximum early on Saturday 6th, meaning long Moon Windows and high peak elevation. Path losses are at their lowest, but increasing during the week. 144 MHz Sky noise is moderate over the first weekend, but low for the upcoming week.
G3YLA JIM
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G0KYA STEVE
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