Propagation News – 17 May 2026

Compiled by G0KYA, G3YLA and G4BAO on 14 May

We hate to start the report on a negative note but we are about to experience unsettled geomagnetic conditions over the next few days.

The culprit is a large coronal hole on the Sun, which rotated into an Earth-facing position on Thursday, 14 May. This large coronal hole, an area with open magnetic field lines, has already been responsible for an increase in the solar wind speed to more than 420km/s.

We can expect it to get worse as the weekend progresses. The hole spans the solar equator so is ideally placed to create maximum disruption to Earth.

If the Bz interplanetary magnetic field swings south, we could see the Kp index rise and maximum usable frequencies, or MUFs, decline. If this happens, expect poor conditions until tomorrow, 18 May.

Meanwhile, the solar flux index declined to 103 on Thursday, 14 May, which starts to put us in a difficult spot.

Usually, we say that a solar flux index of 100 or more is needed for the 10m band to open. So it may be that you’ll need to move lower in frequency for reliable HF openings.

DX to be worked next week includes 3B9IDX from Rodriques Island, T31TTT on Kanton Island, the last few days of XT2AW from Burkina Faso, and FO/F6BCW in French Polynesia.

The Propagation Studies Committee’s space weather station at Baldock identified a solar flare on Sunday, 10 May. The Doppler Flash, or Sudden Frequency Deviation, was triggered by an M5.7 solar flare that began at 1319UTC.

While ‘Flash’ is a good term for the fast-rising edge, the GB0PSC receiver has captured fine detail on the 20MHz signal from the WWV station in Colorado, showing multiple oscillations over a few minutes.

X-ray radiation from the flare quickly increased absorption in the D region, reducing signal levels into the noise after ten minutes.

But those minutes are crucial as they provide data to test whether X-rays or extreme UV from the flare were responsible for the Doppler shift and propagation anomaly.

Next week, NOAA predicts that the solar flux index could rise to be in the 120 to 130 range, which puts us back in the fun zone.

Unfortunately, and for the reasons mentioned earlier, we can expect to see a Kp index of 5 this weekend, but it will eventually decline to perhaps 2 or 3 as the week progresses.

VHF and up propagation news

Compiled by G3YLA and G4BAO

The background pattern of unsettled weather remains with us for a while over the UK as a whole but subtle changes from a cold northerly to a warmer southerly wind will bring higher temperatures back again.

To end the previous week, the cold northerly has brought some heavy showers with hail and thunder in places and the GHz bands will have seen some rain scatter opportunities.

The transition to a more southerly origin of the air will be taking place over this weekend and, although high pressure develops later in the week, we may have to wait until after midweek for any chance of tropo.

The next few weeks encompass a couple of minor meteor showers, the Tau Herculids and daytime Arietids, to add to the random background input.

There should be something to interest those looking for meteor scatter activity and of course it all contributes to the ‘fuel’ for Sporadic-E, which is largely comprised of meteor ionisation.

The solar activity has recently been offering a few minor enhancements of the Kp index but no great results on the aurora front.

Sporadic-E has been producing results on 6m digital modes where there have been brief openings to VK, XT, DU2 and the USA for those lucky enough to catch them.

The usual technique of checking during the two main activity windows of mid-morning and late afternoon should improve your chances.

If you have an opportunity to look at the jet stream patterns, it can be worthwhile trying paths that cross these since it’s believed they are good sources of atmospheric gravity waves that can reach the E region to aid the production of Sporadic-E.

EME now. With maximum declination, the period of longest moon windows, now almost coinciding with perigee, the period of lowest path loss, conditions are at their best for the northern hemisphere.

Moon declination is positive, reaching maximum tomorrow, 18 May. Path losses are at their lowest as we reach perigee today, 17 May. 144MHz sky temperature is low all week.

Category: GB2RS Propagation News