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RSGB
RadCom Assistant Editor | September 18, 2026
Compiled by G0KYA, G3YLA and G4BAO on 17 September, 2026
Thursday, 17 September, marked a milestone in terms of the solar flux index. On this day the solar flux index fell to 100.
This is more psychological than important but it is a sign that the solar flux index is falling from the dizzying heights of more than 300 that it reached at the height of solar cycle 25 two years ago.
The solar flux index briefly dipped to 99 on Sunday, 13 September but it probably won’t be too long before we see it dropping further.
The declining solar flux index has been helped somewhat by better ionospheric conditions as we head towards October.
The lower solar flux index has also been slightly compensated for by relatively good geomagnetic conditions. The Kp index hit a peak of 4 on Monday, 14 September, but has otherwise been around 1 or 2.
Daytime maximum usable frequencies, or MUFs, over 3,000km have been hovering around 21MHz and nighttime MUFs over 3,000km have been around 7 to 10MHz.
But don’t ignore 24MHz as we may see the occasional daylight DX opening. We may expect the daytime MUFs to increase slightly as the month progresses.
DX to be worked this week includes 5W0AF from Samoa; RI1FJZ from Franz Josef Land; FR/F1TEQ and FH/F1TEQ in Reunion and Mayotte; KH8WW in American Samoa; PJ2/K5SL from Curaçao and 8Q7JH in the Maldives.
Later in the week look for KH0/JR1FKR from Saipan and N7NU/VP9 and VP9I in Bermuda. So there is plenty of DX to search for next week.
We expect the solar flux index to hover around 100 over the next seven days, but watch out for poor geomagnetic conditions from Thursday, 24 to Sunday, 27 September, when NOAA forecasts that the Kp index could hit 5.
VHF and up propagation news:
Compiled by G3YLA and G4BAO
The period of unsettled weather that has brought much-needed rain is just about done for a while since it looks like high pressure will build across southern UK today, 20 September.
It may even produce some ridging over northern Britain so there is a good chance for tropo in many areas at some stage during the coming week.
Admittedly, the high gradually edges away to the east by the end of the week but will still be close enough to provide further lift conditions, especially across the North Sea to the Baltic and south to France.
Don’t forget to try calling CQ on SSB or CW in case conditions are up. It’s easy to miss a new square unless you are checking remote beacons to see how the lift is developing.
The far northwest of the UK will have some occasional rain at times and may miss out on the enhanced lift conditions, especially after midweek.
For meteor scatter, it is largely a case of trying to catch the best of any random activity. This means checking conditions in the early hours of the morning.
The solar activity has produced slightly elevated geomagnetic activity with a Kp index up to 4 at times.
With the possibility of a minor storm in the second half of the last week, it probably should remain a watching brief in case we find an unexpected auroral opening, which would tend to favour the equinoxes due to the Russell-McPherron effect.
EME now, and Moon declination starts rising again after its lowest point on Friday, 18 September. Meanwhile, path losses start falling again after apogee, also on 18 September.
144MHz sky noise starts the weekend high, falling back to low by Tuesday, 22 September, where it remains for the rest of the week.
If you are coming to National Hamfest, call in and see the RSGB Propagation Studies Committee stand.
(Mike Terry, UK/BDXC)
