Propagation News – 5 November 2017

Last week saw more settled geomagnetic conditions and, although there were few sunspots, the ionosphere was able to offer DX contacts. The CQ Worldwide Contest saw 15 metres and even 10 metres providing openings at times. With the solar flux in the low 70s it was the seasonal upturn, due to change in ionospheric chemistry, that was mostly responsible for the better conditions.

There is also evidence that coronal hole activity may be responsible for an increase in the ionospheric electron count. This shouldn’t be confused with the effects of a coronal mass ejection, when the Earth is effectively blasted with a high-speed solar wind, which can lower ionization levels and depress maximum usable frequencies.

NOAA issues what are called ALTEF3 warnings when energetic electron levels exceed a certain event threshold. HF propagation enthusiasts might want to experiment and see if these coincide with higher maximum usable frequencies and openings when the solar flux index remains otherwise low.

Solar activity is predicted to remain at very low levels next week with no visible Earth-facing sunspots at the time of writing. However, another coronal hole will become geoeffective and NOAA predicts that its effects could see the K-index rise to five or even six from Tuesday the 7th to Friday the 11th.

Look out for the possibility of initial ionospheric enhancements, but also the likelihood of unsettled conditions and depressed maximum usable frequencies thereafter. However, an increased solar wind can often bring unpredictable ionospheric effects, so do check the upper HF bands for openings all week and keep an eye on the live ionosonde data at propquest.co.uk.

VHF and up

The enhanced tropo of last week saw some good VHF and microwave bands DX, but it will decline quickly as a cold front moves south and destroys the subsidence inversion. This weekend has a colder northerly flow controlling the weather. This means strong shower development around the coasts, especially of Scotland, Northern Ireland and eastern England.

These showers are driven by the warmth of the surrounding seas, whose temperatures change little from day to night. This can provide a 24-hour run of potential rain scatter on the microwave bands. You can track the showers on any rainfall radar to get the beam headings you need.

The next item for attention could well be the return of high pressure in the south late in the week, but this is not supported by all weather models, so check the charts after midweek for signs of a ridge building from the Azores high towards Biscay and southern UK.

The Moon reaches perigee on Monday and maximum declination on Wednesday. This brings low losses and long moon windows for EME, coinciding with microwave bands activity from Cape Verde this weekend until Tuesday.

There are no significant meteor showers this week, but the big Leonids shower is less than two weeks away, so focus on checking all your systems. You can continue to look around dawn for the best chance of QSOs via random meteor scatter.

Category: GB2RS Propagation News