Propagation News –14 July 2024

We had another week of reasonably settled geomagnetic conditions and a high solar flux index.

The solar flux index was at 214 on Thursday 11 July, while the Kp index has been around 2 to 3 all week. That’s generally good news for HF.

However, a small coronal hole is now facing Earth and a solar wind stream flowing from this zone was predicted to reach Earth by the 13 July. This could result in an elevated Kp index and lower maximum useable frequencies, or MUFs for short. It probably won’t last too long, so expect conditions to be back to normal by tomorrow, the 15 July.

Active region 3738 is dominating the Sun’s surface but has only been the source of minor C-class solar flares and will remain a threat for moderate M-class flares. All other regions have been mostly stable.

The daytime MUF over a 3,000km path has often exceeded 24.9MHz, with some better-equipped stations reporting contacts into Australasia on the 10m band.

Nighttime MUFs over a similar distance are still consistently above 14MHz. Make the most of this as they are likely to drop as we head out of summer and into autumnal conditions.

The MUF is extrapolated from the Dourbes [DORB] ionosonde data and should only be used as a guide – it may often be higher, especially in some directions.

The most sought-after DX this week has been K8K/K8R in American Samoa. The DXpedition is testing out all systems on all bands, using CW, SSB and FT8, ahead of the upcoming Jarvis Island DXpedition. The station has been worked from the UK on the 30 to 10m bands, mainly by well-equipped stations, and has been testing the FT8 Superfox mode with some success.

Otherwise, contestants in the RSGB’s 80m SSB Club Championship on Wednesday 10 July reported fair conditions, but a very, very noisy band. Noise is often a limiting factor, especially on the lower HF bands.

Next week, NOAA predicts that the solar flux index may decline to the 180 to 190 range. Geomagnetic conditions may be unsettled today, the 14 July, with a Kp index of 4 at times. The second half of the coming week should be more settled, as long as we don’t have a coronal mass ejection.

VHF and up

The overall picture is of unsettled weather still being around for the coming week, but there will be some temporary moments of weak high pressure to alleviate incessant rain.

As we end the current week, pressure will rise over western areas bringing a chance of Tropo for paths down the Irish Sea and across Biscay. There will also be a second period of high pressure for a time in the middle of next week, favouring the south. This gives us at least a chance of Tropo for this week’s UK Activity Contests on the 23cm and 4m bands.

The ‘unsettled’ part of the story is worth noting, especially if we get some heavy thundery downpours, which should be great for rain scatter. Continuing with scatter modes, there is always meteor scatter as a diversion and the advice is to look in the early hours before daybreak when random meteors are more likely.

Solar conditions are still not entirely settled so there remains a chance of aurora should the Kp index rise to 5 or more. The Sporadic-E season is still doing good business within Europe, but it feels as though it’s not been quite so noticeable as during June for UK stations.

The jet stream pattern is trying to help next week with several useful segments over northwest Europe, which should improve the chances of Sporadic-E paths from the UK into the continent.

Moon declination went negative again on Friday 12 July, which also corresponds to apogee, the point at which the Moon is furthest from Earth. So, Moon peak elevation and path losses will continue to fall again next week. 144MHz sky noise starts low early next week rising to a high of 2100 Kelvin on Friday.

Category: GB2RS Propagation News