RSGB
RadCom Assistant Editor | April 10, 2026
Compiled by G0KYA, G3YLA and G4BAO on 9 April, 2026.
After a pretty stormy run-up to Easter, from a geomagnetic disturbance point of view, the Sun has been quieter. In fact, the Kp index has been below 3 all week. Unfortunately, the solar flux index has also declined, standing at 108 on Thursday, 9 April.
The only advantage has been a lack of solar flares. There have only been 12 minor C-class flares over the past three days compared with 29 C-class flares and six M-class flares on 4-5 April.
We always look for a low Kp index over a higher solar flux index for better HF conditions.
So how does this all affect HF propagation? The maximum useable frequency, or MUF, over a 3,000km path has been struggling to get up to 28MHz on most days. This leaves only 21MHz and 24MHz open after the initial post-dawn ionospheric build-up.
This doesn’t mean that 10m is dead but it may be that the band is only open to DX and not open to Europe.
This may change once the Sporadic-E season starts but we are still a month away from that.
DX being worked, according to the CDXC Slack group, includes 5W1SA in Samoa on 17m FT8, F0/F6BCW from French Polynesia on 12m CW and 3DA0TM in Eswatini on 20m USB. T31TTT on Kanton Island, Central Kiribati, has also been spotted on the 20 and 30m bands using FT4 and FT8.
The DXpedition is focusing on FT modes, although the team is also operating some CW.
Next week, NOAA predicts that the solar flux index will start around 105 but will increase a little over the week to reach the low 120s.
Geomagnetic conditions are forecast to be quiet, with a maximum Kp index of 3 once we get over this weekend’s predicted disruption, which has a forecast Kp index of 5.
Then we are in for a rough ride next weekend, with a predicted Kp index of 6 on 19 April and disrupted conditions for three days. This is likely due to the return of active region 4392, which produced a coronal mass ejection that hit the Earth and caused the Kp index to rise to 7 on its last rotation.
VHF and up propagation news from G3YLA and G4BAO:
The warm, dry weather of the middle of last week has left us with ideas of spring but it has now been replaced by cooler, unsettled weather with rain or showers.
In fact, the next week or two will be generally unsettled, not atypical of April. This will be a good period for rain scatter on the upper GHz bands since April showers can be heavy and present good scatter opportunities.
This unsettled weather means tropo retreats into the background for this period.
Meteor scatter is still under the influence of random activity and best in the early morning hours. Aurora is currently looking more promising with solar conditions offering coronal holes and possible auroras as a result.
Sporadic-E will start to make an appearance soon, especially on the 10m band, but realistically, we probably need to wait until we are into May before chances are more rewarding for the 6m band.
It is often a feature of the early part of the Sporadic-E season that the traditional two periods of activity of the high season, morning and afternoon, start off as one broad period around the middle of the day.
For EME operators, Moon declination is starting to climb again, going positive on Wednesday, 15 April. Earth-Moon-Earth path losses are past maximum now and continue to fall all week.
144MHz sky noise is high today, 12 April, and will fall to low for the rest of the week. Friday, 17 April will be an exception as the Moon and Sun will be close in the sky.
(Mike Terry/BDXC)
