Propagation News – 2 May 2021

| April 30, 2021

Last week was characterised by relatively low sunspot numbers, but reasonably settled geomagnetic conditions. The solar flux index never rose above 80 all week, despite a large cluster of sunspots. This cluster, composed of regions 2818, 2820 and 2821, were responsible for some C-class solar flare activity, but never really grew into anything. By the time you read or hear this they will have rotated out of view.

The Kp-index started the week at five, thanks to the effects of a high-speed solar wind stream from a coronal mass ejection. This was relatively short-lived and the rest of the week saw more settled conditions with a maximum Kp-index of three and often zero.

HF conditions have been variable. There has been DX workable, as Norfolk ARC showed during last Saturday’s International Marconi Day. GB0CMS made more than 900 contacts on HF, including contacting the Dominican Republic, the Philippines, Ecuador, Panama, the Falkland Islands, Australia and Indonesia. SSB activity on 10 metres has been reported as being relatively quiet, with the odd sporadic E contact into Europe. FT8 has thrown up a few contacts into South America during late afternoon and early evening.

Next week, NOAA predicts the SFI may dip again, perhaps down to 72-73. This weekend may see unsettled geomagnetic conditions with the potential for the Kp-index to rise to four or five due to coronal hole activity. However, once this clears we may expect a more settled Kp of two as the week progresses. Propquest shows that, according to the Chilton digisonde data, daytime MUFs over a 3,000km path are generally reaching the 18MHz band and occasionally 21MHz.

VHF and up

Next week it will probably be very difficult to time the weather changes correctly. It will be a mix of classic April showers—in May!—and some longer periods of rain, but also weak ridges of high pressure or, more accurately, ‘cols’, between highs and lows. These are very rarely useful for tropo, but may facilitate temporary lifts in early mornings. The trend towards a showery weather pattern is likely to be good news for the rain scatter operators on the GHz bands.

With the arrival of May, expectations for sporadic E grow stronger. The daily blogs will begin this month on the Propquest website where a commentary about the location of jet streams and potential for sporadic E will be discussed, along with a chance to evaluate the new sporadic E probability index, or EPI, shown on the same website. Beams certainly help with weak sporadic E or multi-hop paths, but a strong opening will be found with even a colinear, so it’s not just for super-stations. If you’ve never worked sporadic E before, doing just one thing, checking 10m and 6m at teatime, will guarantee you the best chance of breaking your duck.

Last week we had a supermoon. No reason to get excited, this is simply a full Moon occurring within 10 percent of perigee. Perigee was last Tuesday so EME path losses will slowly rise all week. Moon declination is negative until Saturday so we’ll see lengthening Moon visibility windows and peak Moon elevations as the week goes on.

Two meteor showers to look out for this week. The Eta-Aquarids has a broad peak around 6 May with a good zenithal hourly rate (ZHR) of 50, then the much smaller Eta Lyrids on the 8th.

Category: GB2RS Propagation News