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The K7RA Solar Update

RSGB
January 18, 2019

At the risk of sounding like a stuck record, the Sun remained spotless this past week with a solar flux index stuck firmly around the 70 mark. Geomagnetic conditions were mostly settled with a maximum planetary K-index of four, although on average it was usually much lower than this, around one or two.

Many are bemoaning the poor HF conditions and it is not surprising. Although there are openings up to 21MHz at times, the 20 metre band is more likely to bring you reliable DX contacts than the higher bands. We can’t expect to see much action on 12 and 10 metres until the sporadic E season starts in early May.

The lower bands are still throwing up some surprises though and transatlantic contacts on 160m are still worth chasing if you are equipped for Top Band. Eighty, 40 and perhaps even 30 metres may also bring you some DX during darkness. As always, we encourage you to use the online tools at predtest.uk and propquest.co.uk to plan your activity.

Next week, NOAA predicts more of the same with a spotless Sun and a solar flux index of around 71. Geomagnetic conditions should remain quiet, until the 24th and 25th when material from a recurrent solar hole may push the Kp index to five, bringing the potential for aurora-like conditions and depressed maximum usable frequencies.

VHF and up:
There is unlikely to be much tropo this week. A key feature of the weather is an area of low pressure which drifts south-east across the country from Greenland on Sunday to Iceland, then Scotland, and arriving over England by Wednesday. Looking at its origin, it will herald a spell of cold weather with a taste of winter for some areas. This may provide wintry showers in some places to give a chance of rain scatter on the GHz bands, but it’s not a great opportunity.

That leaves the last part of the week to consider, after the cold winter low has moved away into the continent. Models suggest a return of a ridge of high pressure, some models stronger than others. But it will be building in dry cold air, which is not good for creating a strong moisture contrast across the temperature inversion and thus not a great signal for tropo.

So overall, probably a flat feel to the week regarding VHF/UHF weather propagation, but with the Eshailsat-2 geostationary transponder undergoing engineering tests as we write I’m sure many will be focussed on this.

The Moon reached maximum declination this morning and perigee is tomorrow, so it’s a good week for EME.

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