U.K. Propagation Update, February 21

 

RSGB

GB2RS News Team

February 21, 2025

It seems we were a little over-ambitious in suggesting that last week would be better for HF propagation. It looked like we would avoid coronal mass ejections and see the Kp index fall to lower levels.

Unfortunately, the Sun had other ideas and a fast-moving solar stream, often moving faster than 500 km/s, had a south-pointing Bz, which coupled more easily with Earth and sent the Kp index up to four or more.

So even by Wednesday 19 February the Kp index was hitting five.

But it seems that the geomagnetic disturbance merely lowered the MUF from around 40-45MHz to 31-32MHz, so it barely affected HF propagation.

At the time of writing there had only been one M-class solar flare in the past five days, but more than 50 minor C-class events. There were no Earth-directed CMEs.

Nevertheless, there was DX to be had with the standout stations being the V73WW DXpedition to Majuro Atoll on the Marshall Islands, TI1RRC Costa Rica, and 5N9DTG in Nigeria. Upcoming DX next week includes OX3LX (Greenland), Dave G4BUO as 5W0UO (Samoa), TO3Z (Guadeloupe), 4S7SPG (Sri

Lanka) and FS/VA3QSL (St Martin).

Next week, NOAA predicts that the week commencing the 23 February could see the solar flux index starting at 170, but then rising to 195-200 as the week progresses. Geomagnetic conditions are predicted to start quietly, with a Kp index of two, but then become unsettled by the 27 to

29 February, with a maximum predicted Kp index of five.

If this scenario does pan out then we may expect the best HF conditions to occur at the beginning of next week, from the 23 to 26 February.

As always, keep an eye on solarham.com for day-to-day solar news, and perhaps monitor PSKreporter, the Reverse Beacon Network and DX Clusters for digital, CW and SSB HF propagation updates.

VHF and up :

The current spell of unsettled weather seems likely to continue through to the end of next week. There will also be significant windy weather at times. It is therefore not a particularly good period for Tropo, or big antennas for that matter.

This leaves us with rain scatter on the GHz bands and some of these scattering regions will be large areas affecting the whole of the country as active weather fronts pass by, rather than more isolated and harder-to-follow showers which often provide our rain scatter.

Meteor scatter is still within its quieter period with no major showers and better chances coming from random meteor activity, which tends to peak in the hours before dawn.

Recent solar activity has provided some weak auroral conditions on many days.  As usual, check for high values of the Kp index as a good indicator, or even listen for a watery tone on the LF bands. Ultimately you will need to see the Kp index going to at least five to make it worth checking for auroral signals on VHF.

We are still in the dormant period for Sporadic-E propagation, which is a shame in view of the powerful jet streams likely during this stormy weather. These would produce good Es prospects in the main summer season, but weaker Es at low VHF are still a possibility despite being out of season.

Moon declination is at minimum today, Sunday 23 February, and path losses are decreasing as the Moon moves closer to Earth as it heads to perigee on Saturday 1 March. 144MHz sky noise goes high this weekend, beginning Saturday 22 February.

https://rsgb.org/main/blog/news/gb2rs/propagation-news/2025/02/21/propagation-news-23-february-2025/

(Mike Terry, UK/BDXC)

UK Propagation Update

 

RSGB

GB2RS News Team | September 13, 2024

Last week showed that HF conditions are improving as we head into the autumn.

With a solar flux index still above 200, there was plenty of DX available to work. CDXC members reported working VP6WR on the Pitcairn Islands, KH8T on American Samoa and 3D2USU on Fiji, which is not a bad catch for early September.

A little closer to home, 9A168TESLA in Croatia has been popping up for short periods celebrating the 168th anniversary of the birthday of electrical pioneer Nikola Tesla. Watch DX Summit closely for operating times.

The daylight maximum useable frequency, or MUF, over 3,000 kilometres remains above 28MHz on the whole, although a raised Kp index tends to reduce this.

Geomagnetic conditions remained relatively calm with the Kp index below

3 all week. That changed on Thursday 12 September as material from a coronal mass ejection, or CME, passed the ACE spacecraft in the early hours.

The solar wind speed increased to more than 500 kilometres per second and the Bz swung south. On Thursday 12 September, the Kp index was 5 and the Met Office Space Weather department was forecasting potentially unsettled conditions for this weekend, ending today the 15 September.

At the same time an X-class flare occurred, with lowered MUFs due to increased D-layer absorption.

Two large coronal holes on the Sun’s surface are also now Earth-facing and threaten to add to the solar wind this weekend.

According to NOAA’s predictions, the solar flux index should stay in the

210 to 225 range next week, although a large number of spots are about to rotate off the Sun’s visible disk.

This may be compensated by an active region that’s about to rotate into view. This has been emitting C-Class and lower-level M-flares and could potentially be the same region that produced a number of energetic eruptions off the far side of the Sun over the past week. Time will tell.

VHF and up :

The heavy showers at the end of last week produced some good rain scatter, but no QSOs in the UK were noted due to the showers not coinciding with GHz contests and few suitable home stations were active to take advantage of them.

After a gradual build-up of pressure over this weekend, ending the 15 September, high pressure is suggested by most models during the coming week. However, there is some uncertainty about the position of the high.

Currently, models are favouring the north of Britain and this means that in the south, although still on the edge of high pressure, there could be a brisk northeasterly breeze, which may weaken the inversion prospects. It’s not clear if the Tropo will be functioning in time for the 70MHz Affiliated Societies Contest today, the 15 September, but should be helpful for the 1.3GHz UK Activity Contest on Tuesday 17 September and the 70MHz UK Activity Contest on Thursday 19 September.

Solar conditions are still likely to offer the chance of the occasional elevated Kp index, which is a good sign of possible aurora. It will be interesting to see how things evolve this weekend, ending the 15 September, as a series of expected CMEs are due to reach earth.

The amateur bands between 10m and 2m are the ones to check as well as looking out for ‘watery’ sounding signals on the HF bands. Remember it doesn’t have to be dark for radio aurora, so don’t wait for dusk before checking.

Meteor scatter is mainly down to random activity in the coming week. 

However, with the September Epsilon Perseids stream still active until the 21 September, having peaked on the 9 September, conditions may be slightly enhanced.

For EME operators, Moon declination is negative but rising and going positive again on Wednesday 18 September. Moon visibility windows will continue to rise while path losses decrease as we approach perigee on Wednesday 18 September. 144MHz sky noise is moderate for the whole of next week.

https://rsgb.org/main/blog/news/gb2rs/propagation-news/2024/09/13/propagation-news-15-september-2024/

(Mike Terry/BDXC)