Propagation News – 27 August 2023

Last week saw plenty of DX being worked, thanks to quiet geomagnetic conditions and a seasonal change to a more autumnal ionosphere.

Although we are still in August, there are signs that the ionosphere is moving away from its summer doldrums as its chemical composition changes to more monatomic species, which ionise more easily.

Another bonus is that there has been a big reduction in the size and number of coronal holes on the Sun, which again leads to lower Kp indices.

Mike, G8AXA reports that, for the first time in a long while, his Faros IBP beacon monitoring software recorded the VK6RBP beacon on 28.200MHz between 0857 and 1000UTC, via short path, just making S1 on his long wire and Yaesu FT-991A. On 21.150MHz, he also recorded hearing the ZL6B beacon between 0757 and 0909UTC up to S3.

Conditions should continue to improve as we move towards September and October.

Last week, the solar flux was in the 140s and 150s. The Kp index never rose above three, meaning the ionosphere was quite stable. The proton flux was also very low. FT8 on the 15m band was humming in the afternoon with the Far East and Caribbean both being workable at the same time.

Next week we have active regions 3413 and 3415 rotating to be more Earth-centric. NOAA predicts that the Solar Flux Index will rise to the 160s again and the quiet geomagnetic conditions may continue with a predicted Kp index of two.

So, as long as we don’t get any solar flares, or CMEs erupting from sunspot groups 3413 and 3415, we could have a good week again for HF DX.

VHF and up

The current spell of unsettled weather looks likely to stay with us for most of next week, in fact until around Friday when there are signs of a ridge building in for next weekend, although mainly for southern areas.

This could be in time for some tropo over the weekend of the 144MHz Trophy Contest. However, the models are a bit uncertain this far out, so keep a watch for changes during the week.

The remaining mode in such unsettled weather is of course rain scatter and most of the period until the end of the week should provide many opportunities.

As we approach the close of the traditional sporadic E season—although it can still occur in any month—the activity levels are much reduced after the end of August and certainly tail off sharply after the first week in September. We are still getting the occasional flurry of activity for multi-hop paths on 10m to the Far East and the States, so don’t abandon it just yet.

Remaining modes such as meteor scatter are still available via random meteor activity and there are always chances of a higher Kp index with its implications for aurora. Note that the autumn and spring months are typically a preferred time for aurora.

This Saturday sees minimum Moon declination with the Moon not getting above 10 degrees elevation. It goes positive again next Friday. As the Moon’s perigee is on Wednesday, path losses are at their lowest. 144MHz sky noise is high this weekend, but falling to low levels by next Friday.

Category: GB2RS Propagation News