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Propagation News – 29 September 2019

RSGB

September 27, 2019

Last week continued with zero sunspots, making it now more than 190 days this year that the solar surface has remained spotless. Many solar scientists predict that 2019 will have a total of more than 250 days without sunspots, which would make it the ninth most ‘spotless’ year since records began in 1849. Current research suggests that it may be at least next summer before we see Solar Cycle 25 taking off. Solar physicist Lisa Upton says the current solar minimum will continue through 2019, likely ending in 2020. The next solar maximum is expected in 2024-2026. Meanwhile, looking at HF propagation last week there were a few surprises. Ten metre FT8 showed that there are still some short sporadic E openings occurring on the band. The trick is to be there when they happen!

Daytime critical frequencies are still hovering around the 4.1 to 5.1MHz range, which is good news for 80m local contacts, but not so good for 40m. These figures translate to maximum useable frequency over a 3,000km path of up to 18-19MHz at times. But do keep an eye on propquest.co.uk for real-time figures.

This weekend will likely see the after-effects on the ionosphere of a very large coronal hole that was spewing out solar matter when this report was being prepared. This may send the K-index up to a maximum of six, with lowered critical frequencies and noisy bands. The rest of the week will see slightly more settled conditions.

The good news is that DX is starting to return as we move towards better autumnal ionospheric conditions. The lower bands are also starting to come into their own, and as we have passed the Autumnal Equinox, don’t forget that this is also the best time of year for north-south, transequatorial contacts.

VHF and up:

There was a totally different feel to the weather last week with a return of rain, showers and strong winds at times. That produced some nice rain scatter QSOs on 10GHz for the SHF UK Activity Contest. It looks like a similar story this weekend and into much of the next week for most areas, which will mean that rain scatter is again an item for the coming week. There will be a brief possibility of a weak ridge of high pressure crossing the country midweek, although such short duration transient features are not usually great providers of tropo.

This Sunday, the Moon is at perigee—its closest point to Earth—so path losses are low. Declination is negative and falling, so peak moon elevation will get lower as the week progresses. We are entering a period in the Northern Hemisphere where Moon perigee coincides with low and decreasing declination, meaning that lowest path losses coincide with low Moon peak elevation and short Moon visibility windows. This trend will continue until June 2022, when perigee and lowest declination coincide. After this, the trend reverses until September 2026 when perigee and maximum declination coincide again. This is a double-edged sword, as the upcoming conditions will favour extreme EME DX where antenna elevation needs to be very low, but path losses on the GHz bands will be highest when the Moon is at its highest. There are no significant meteor showers this week, so continue to check the early hours before dawn for the best random meteors. (rsgb.org)

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