Propagation News – 20 December 2020

We’ve had another week of lacklustre sunspot activity. The solar flux index has been pegged at around 82, caused by the two tiny sunspots in active region 2793. Having said that, a lack of coronal hole activity has meant that geomagnetic conditions have been settled, with a maximum Kp index of two, but more often than not it was actually at zero. This has meant that the daytime critical frequency over the UK has frequently been around 5.5MHz. This means a maximum usable frequency over a 3,000km path of around 21MHz, with very occasional openings on 28MHz.

Even 10m FT8 has been sounding quiet, with intra-UK signals being most prevalent. You can often see 10m FT8 ground-wave signals up to around 100 miles away being decoded.

We did have a C-class solar flare on Monday the 14th, but as it was in the afternoon with sunset only an hour or so away it didn’t do too much damage, with the ionosphere recovering very quickly.

Next week, NOAA predicts the SFI will be at 85 to 86. The effects of another coronal hole will likely be felt across this weekend, with the potential for the Kp index to rise to four. But after that subsides, geomagnetic conditions are likely to be more settled, with a maximum Kp index of two over the Christmas period.

Santa Claus is taking a rest this year at OF9X in Finland, but we do have some other Christmas DX for you to chase. The CQ Santa Net is held in the USA on 3.916MHz every day at 0115UTC. There is a chance you may hear it, depending upon who is operating, as December is generally a good month for transatlantic low-band propagation – just ask Guglielmo Marconi, who traversed the Atlantic on the 12th of December 1901!

Please note that amateurs in the UK cannot transmit on 3.916MHz as it is outside of the UK allocation, but you may be able to hear the net taking place.

VHF and up

We continue through this first weekend with the unsettled theme to the weather giving wet and windy conditions at times so again it’s a good period to test out some rain scatter paths on the GHz bands. A major change is shown in some models from midweek as high pressure edges towards Ireland from the Atlantic and puts a colder northerly flow down across the British Isles from midweek. This will not be useful for Tropo, since the high remains well to the west, but it will allow some showers to affect many areas and it’s not totally out of the question that some could have a wintry flavour in the second half of the week.

At the end of next week the high moves in across the country, but it’s still unlikely to be a strong Tropo player.

The Geminids meteor shower has peaked. Activity was high, with stations running just 50 watts and a small beam reporting good digimode meteor scatter QSOs. The Urisids shower peaks on Tuesday with a ZHR of 10 and there’s not long to wait until the next big one, the Quadrantids, in January. More about that shower in the next report.

Moon declination goes positive again on Tuesday so visibility windows are increasing all week. Losses are increasing as we move away from perigee, but 144MHz sky noise is low, not reaching 400 kelvin until next Sunday.

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

Category: GB2RS Propagation News