Propagation News – 18 August 2019

We had more of the same last week with zero sunspots, but no geomagnetic disturbances. The good news is that there appear to be no Earth-facing coronal holes coming around the Sun, although there are significant holes around the solar polar regions.

The tool at Propquest.co.uk has been showing an interesting phenomenon over the past week. It appears that the critical frequency, and therefore maximum useable frequency, have been increasing after sunset. This means that the higher HF bands, such as 20 or even 17m, may be staying open longer. It also means that 80m is often open for UK contacts after dark, at least until nearly midnight. Daytime DX is still a little harder to come by as D-layer absorption still reigns supreme, but it is worth looking for greyline contacts around sunset.

Next week NOAA predicts the solar flux index will be at 67 and the geomagnetic K index will be at two. This means we can expect 20 or perhaps 17m to be the highest bands in use, other than contacts via Sporadic-E, which is now declining as we head towards September.

VHF and up

The recent run of unsettled weather has produced some heavy thundery downpours in places and some nice rain scatter propagation across the UK on the microwave bands. This weekend is looking like more of the same, but as pressure builds again in the south it’ll change to Tropo as the preferred mode for paths into the continent. Northern Britain will however remain nearer the low pressure and provide a few further options of rain scatter.

Sporadic-E is putting in the odd appearance on 10m, 6m and 4m, but getting very hard to find now. Next week should start with the best chances with a jet stream over the near continent, but this will probably weaken later, so focus on the first half of the week.

As we move away from the peak of the Perseids meteor shower, don’t feel all is over, as it’s a broad peak and always worth exploring meteor scatter propagation if you haven’t tried it yet.

The Moon was at apogee yesterday so EME path losses are at their highest this weekend. They will fall as the week progresses and with declination going positive again late on Monday, Moon windows will lengthen and the Moon’s peak elevation will increase all week.

And that’s all from the propagation team this week.

Category: GB2RS Propagation News