Propagation News – 6 December 2020

| December 4, 2020

What a great week it was for HF propagation. We started it off with the CQ Worldwide CW HF contest, which saw some DX openings up to 28MHz and solid DX being worked on 21MHz. The only downside was an M-class solar flare, which was launched off the Sun on Sunday. It was a big one, but luckily it didn’t affect the UK. The eruption in the sunspot occurred when the sunspot was not pointed toward Earth. This does, however, serve as a warning that we can expect more solar flares over the coming years as Solar Cycle 25 progresses.

The rest of last week saw the Solar Flux Index decline slightly to 105 by Thursday. Nevertheless, daytime maximum useable frequencies were generally above 21MHz for a lot of the time, with occasional openings on 28MHz.

Next week NOAA predicts that the solar flux index will decline to the 90s and then the low 80s as the week progress. However, active region 2790 has rotated to be Earth-facing and this may keep the SFI higher than predicted – only time will tell. On Thursday another potential active region was also coming into view. If it develops, we could see the SFI in the high 90s or even topping 100 once again.

The good news is the Kp index is predicted to remain low, reflecting the more settled geomagnetic conditions. A large coronal hole will become Earth-centric by the 5th, which could result in an elevated Kp index at the end of the weekend – although this will be dependent on how the Bz field of any solar wind is oriented. A south-facing Bz field more easily couples with the Earth’s magnetic field, letting solar particles enter the ionosphere. Only time will tell.

VHF and up

Not much terrestrial VHF propagation to look forward to this week, with things looking cold and unsettled. A slack low-pressure system will occupy the British Isles for much of the next 10 days, so I wouldn’t build up any Tropo hopes. The general unsettled nature of the weather pattern means that rain scatter could be the mode of interest for the GHz bands. You might also find some snow static raises noise levels a bit in some parts of the country.

December is a hot month for meteor scatter. The Puppid-Velids, with a Zenighal Hourly Rate of 10, peaks tomorrow, and the Monocerotids with a Zenithal Hourly Rate of three peaks on Wednesday. These are just an hors d’oeuvre for the Geminids shower, just over a week from now, on the 14th. With ZHR of a whopping 150, the Geminids is usually the best one of the year. Even now the meteor rates will be climbing so if you have reasonable power and a beam for 2, 4 or 6m, get looking for JT mode DX.

It’s a good week for EME too with Moon declination high but declining. We still have long visibility windows all week, with falling path losses until perigee next Sunday. 144MHz sky noise is low at the moment, not reaching 500 kelvin until next Sunday.

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

Category: GB2RS Propagation News